Emperor Otto II confirms the jurisdictions of the bishops of Poreč and grants them immunities.
In nomine Sancte et Individue Trinitatis.
Otto divina favente clementia Romanorum imperator augustus.
Si Ecclesiarum Dei curam gerimus easque dilatare studuerimus, nostri imperii fastigium augmentari minime ambigimus.
Quocirca omnium sancte Dei Ecclesie fidelium nostrorumque presentium scilicet et futurorum noverit universitas, qualiter interventu ac peticione nostri dilecti presbiteri Dudonis ac Andree diaconi nostri benivoli capellani Adam sancto Parentine Ecclesie antistes nostram adiisse clementiam, postulans quatenus nos pro Dei amore nostreque anime remedio nostra preceptali auctoritate omnia predia sue Ecclesie, que antea a nostris antecessoribus imperatoribus, regibus pro suarum animarum remedio prefate Ecclesie donaverunt, qua in basilica Sancti Beatum corpus Mauri requiescit, sive que ab aliquibus Deo devotis fidelibus data sunt, vel que danda erunt, confirmare et corroborare dignaremur.
Cuius dignis postulationibus aures nostre pietatis inclinantes pretaxate Ecclesiae predia nominative:
 Turrim, que est supra piscationem None,
 et illam de Cervaria,
 et castrum Pisinum,
 quod a regibus seu ab Ugone largitum est, videlicet Ruvignum,
 quantum ad Episcopatum sancte Parentine Ecclesie donatum est a nostris antecessoribus, videlicet in loco qui dicitur Duo Castella et Valles
cum omnibus pertinentiis suis iuste et legaliter ad predictum episcopatum pertinentibus nec non villis, terris, campis, vineis, pratis, aquis aqnarumque docursibus, molendinis piscationibus, venationibus, montibus, planiciebus, vallibus, cum omnibus rebus mobilibus et immobilibus que dici et nominari possunt, seu in quocumque loco prenominatus episcopatus terram habet, per hoc nostrum preceptum confirmamus eidem episcopo Adam suisque successoribus et corroboramus.
Precipientes denique iubemus, ut nullus dux, patriarcha, archiepiscopus, episcopus, marchio, comes, vicecomes nullaque regni nostri magna vel parva persona pretaxatum presulem suosque successores de omnibus predictis rebus molestare temptet nec ad ulla placita hominibus supra terram sancte Parentine Ecclesie residentibus, qui ab episcopo reclamationem habent, sine advocato episcopi nullam contrarietatem faciant nec invite ducantur nisi ante presentiam presulis sine legali iuditio, sed liceat eidem presuli suisque succcssoribus quiete et pacifice cuncta sua predia tenere et firmiter possidere omnium hominum contradictione penitus remota.
Si quis igitur huius nostre pagine violator fuerit, quod minime credimus, sciat se compositurum auri boni libras mille, medietatem camere nostre et medietatem prefato presuli suisque successoribus.
Quod, ut verius credatur diligentiusque ab omnibus observetur, hanc paginam propria manu corroborantes sigilli nostri impressione inferius eandem iussimus insigniri.
Signum domni Ottonis secundi serenissimi imperatoris et invictissimi (SM) augusti.
Adelbertus cancellarius advicem Petri episcopi et archicancelarii recognovi et scripsi.
Data VII nonas iunii anno Dominice incarnationis DCCCCLXXXIII, indictione XI, regni vero domni secundi Ottonis XXVI, imperii vero eius XIII.
The charter is only preserved in later copies, the oldest of which is the one featured in the 16th-century Liber iurium episcopalium I of the Bishopric of Poreč. Thus, the potential for possible later interpolation is extremely high, especially bearing in mind the numerous attempts of the bishops of Poreč to assert their jurisdictions over the territories disputed by Venice, the counts of Gorizia and the patriarchs of Aquileia (and their numerous retainers).
The charter has some problematic internal features, namely the dating. First, there is no such thing as "VII die pridie nonas". One solution, proposed already by the editors of the Monumenta Germaniae historica, was that the correct date should be "VII idus iunii" which would concord with the 7th of June, the day when Emperor Otto II was indeed in Verona. Thus, the "VII nonas iunii" is customarily interpreted as a scribal error of the 16th-century copyist, an error that was repeated in all the other subsequent copies.
Another problem is the fact that the dating elements do not concur with themselves: the year 983 anno Domini indeed concurs with the 11th indiction, but the years of Otto II's reign concur with the years 984 (26th of his kingship, crowned king in May of 961) and 980 (13th of his emperorship, crowned co-emperor in December of 967). The correct years should be 25th of his kingship and the 16th year of his emperorship although the original imperial diplomas issued in June of 983 have either 25th year of kingship and 15th year of emperorship (the majority) or the 26th year of kingship and the 16th year of emperorship (cf. docs. 290-317 in MGH, DD O II, pp. 342ff) Again, one can presuppose a copyist error where the 26th year of kingship was calculated as 983 (as in, e.g. doc. 312 in MGH, DD O II, pp. 312-313; generally it seems that chancellor Adalbert dated year 983 with the 26th and 16th years of Otto II's respective reigns) and thus copied correctly, but the original year XVI was erroneously copied as XIII, an easy mistake to make.
The final problem are the territories featured as having been donated to the Bishopric of Poreč by the Italian kings and the predecessors of Emperor Otto II. Namely, no royal or imperial diploma for the Bishopric of Poreč survives prior to this one from 983. Moreover, the phrase "videlicet Ruvignum quantum ad Episcopatum sancte Parentine Ecclesie donatum est a nostris antecessoribus, videlicet in loco qui dicitur Duo Castella et Valles" is not only clumsily styled, but it also fits very awkwardly the enumeration of localities; the sentence could indeed work perfectly well without it:
"Cuius dignis postulationibus aures nostre pietatis inclinantes pretaxate Ecclesiae predia nominative: Montana, Rosarium... et castrum Pisinum, Medelanum, quod a regibus seu ab Ugone largitum est cum omnibus pertinentiis suis iuste et legaliter ad predictum episcopatum pertinentibus nec non villis, terris... per hoc nostrum preceptum confirmamus eidem episcopo Adam suisque successoribus et corroboramus."
Finally, a look at the Mapped Toponyms field shows that the possessions enumerated before the clumsy phrase ("videlicet Ruvignum... Duo Castella et Valles") form a relatively compact territory stretching from Červar and Tar to the north of Poreč, then moving towards Motovun and embracing fort Nigrinjan (between Tar and Vižinada) plus the two localities in the present-day Vižinada (Ružar and Medelin, both places no longer exist today), and finally Pazin in the central Istria as the westernmost territory of the Diocese of Poreč.
Thus, the most logical conclusion seems to be that the Otto II's original confirmation charter was indeed interpolated with the "videlicet Ruvignum... Duo Castella et Valles" phrase as a response to the centuries-long quarrel between the bishops of Poreč and patriarchs of Aquileia over this disputed territory.
The struggle for this territory had begun in the 10th century, but numerous forgeries created by both the bishops of Poreč and the patriarchs of Aquileia make fixing the exact chronology of the fateful conflict almost impossible to ascertain.
The documents that form part of this story arc are the following:
1) Charlemagne's donation charter to the patriarch's of Aquileia from 803 (forgery made by the patriarchs of Aquileia – see the document here);
2) Donation charter of Patriarch Rodoald to the bishop of Poreč from 965 (forgery made by the bishops of Poreč – see the document here);
3) Confirmation charter and the grant of immunity of Emperor Otto II to the bishop of Poreč from 983 (this document);
4) Confirmation of Charlemagne's 803 charter by Emperor Otto III to the patriarch of Aquileia from 996 (authentic charter, but confirming a forgery – see the document here);
5) Sergius IV's papal confirmation of 1010 issued in favor of the bishops of Poreč (authentic papal charter – see the document here);
6) King Henry IV's highly dubious confirmation charter of 1077(?) to the Bishopric of Poreč, confirming Otto II' 983 charter (problematic charter, possibly a forgery – see the document here);
7) King Henry IV's donation charter to the Patriarchate of Aquileia, bestowing upon the patriarchs the regalian rights over the Bishopric of Poreč with the right to appoint and invest its bishops (authentic royal charter – see the document here);
8) Alexander III's papal confirmation of 1177 issued in favor of the bishops of Poreč (authentic papal charter, confirming the bishop's spiritual jurisdiction over the disputed territory, but not secular – see the document here).
In the end it must be stressed that there is no historical record of the bishops of Poreč practicing their secular jurisdictions over Rovinj, Dvigrad or Bale; on the contrary, the patriarchs of Aquileia had been appointing the gastalds of Dvigrad already in 1090s (see the document here), more than a century before they became the margraves of Istria (1209, see the primary sources here, officially confirmed in 1210, see the document here).