There’s also @sheep_nova who does good deals on eBay and even better deals over PM for PGM motherboards and carts (cheap).
You can request whatever revision you need and if there’s a problem he always sorts it out.
Honestly there’s no real need to fuss over PGM motherboard revisions: functionally, gameplay wise they’re all the same. Coin cell batteries can be installed on all revisions and sheep_nova takes care of this detail on the ones he sells.
I think the earlier versions had cart slot pins only on other side of the connector, so that would make them "less reliable" with contact. Not sure thou, I might mix these with something else so correct me if I am wrong.
You’re probably right. But it’s not really a big issue honestly, I own none of the newer PGM motherboards that the Retro Police bang on about, and none of mine have issues at all.