the M2 was the keyboard for the PS/1, it was for a cheaper version of the PS/2 and so is also a cheaper keyboard, but as far as i know it should use the same protocol and have a PS/2 connector (and the PS/2 came before the PS/1). one very common problem with those is bad capacitors on the control board.
as far as the layout go i do agree it is quite strange, especially if you are in the US, to me it looks European, but it does not like to be any standard national layout, although the M and i think M2 could be made to use any layout you liked just by switching keys around, so likely that is what happened here, especially with the french legends on a qwerty layout.
TL:DR to me this is a french or Canadian board with a custom layout and likely buckling springs
