We used to get those ex RAF binos through the workshops after the RAF/RN and Army Ordnance stockpiles and repair facilities were pooled. They were high quality or they hadn't had the hard life/pasting of the Army No2's. There were two sorts with the old RAF stores 6E- classification. The Watsons (I don't know after all this time whether they were related to WWatson of No32 Mk1 and 2 fame) and another with a set of scrolled PB or BP initials that we called 'Berettas' because the PB looked like the PB-Beretta initials on the Malay Army shotguns.
They were obviously based on the old No2 design by Kershaw but apart from the 6BA(?) cover screws, the clamp bars and screws and eye-cups plus the little ocular lens cell unit (that could fit if the ocular end of the thread was slightly undercut) I don't think anything else interchanged.
I feel sure that these RAF ones also came with or without the reticle and also in a sort of Mk2 - without and Mk3 - with purging screws.
Worse still was the Navy assortment of what we called No5 7x 50 'Artillery' binos. I don't think any two pairs were the same and certainly nothing fitted with what we had, not even the OG lens sleeves or ocular prism blocks. Even the little eye cups that would crack with monotonous regularity all seemed to differ. They weren't short of them so it was easy to just scrap theirs and endorse the condemnation certificate with RE-ISSUE followed by the V5/OS- number of the Army 7x 50 No5 Mk5 black (but later, green). But instead of stripping a few of their old Ross and Kershaw 7x 50's for the spares parts. the Navy always wanted everything back, even if the loose bits went back in a poly bag.........., only to be dumped afterwards.
Eventually, the Navy got the black rubber armoured AVIMO binos in both L-11 and L-12 versions. They took great delight in replacing the crap neck strap with that white string stuff they seem to enjoy lashing, knotting and weaving like demons. Unfortunately you couldn't put those L11's onto the collimating block or into the desiccation tank with all that sloppy whitened lashed and knotted cord on them. So it was cut off!