Hello 
I am working on gaining a deeper understanding of the pāṭmokkha across Early Buddhist sects.
It is my understanding that, as far as concerns the bhikkhupāṭimokkha, the (1) Pārājika (2) Saṅghādisesa, (3) Aniyata, and (4) Nissaggiya Pācittiya offences are all nearly identical across every Vinaya tradition, barring the occasional difference in phrasing or minor details. This seems also to be the case with the majority of the (5) Pācittiya rules. The exception here is that some schools have 90 Pācittiyas and others have 92 (the Mahīśāsakas with a middle 91).
Of the schools with 90 Pācittiya rules, the missing offences are the corresponding Pācittiya 23 and Pācittiya 82 of the Theravāda Pāḷi Bhikkhu Pāṭimokkha. These same rules occur in the Mahāsaṁghika Pāṭimokkha(s) and are equally those missing. They are the rules concerning the ovāda, and concerning the designation of Saṅgha property to oneself.
For those in the know, to what extent is this information accurate, and how can it be expanded to provide a fuller picture of the Pāṭimokkha from a cross-comparative perspective. I am slowly working through a side-by-side comparison of individual rules, but would like to develop a more concrete sense of the main content of the rules that is shared, and how. Also: for the missing 2 rules, is there a historical explanation/hypothesis as to why they are missing? Are they subsumed under other rules in the Vinayas with 90 Pācittiyas?
Mettā