purportedly people have had better luck with full height 5.25" drives.
Many moons ago when Weird Stuff was still in business, I spoke to a few people buying 5.25" full height drives in their as-is section. Their claim was that nearly all the drives they bought works just fine.
this looks like somebody's proprietary memory and I/O expansion. the back side of the board isn't visible, the front has no gold fingers on the ISA card edge, so it's safe to conclude that it won't work with anything other than the specific motherboard it was designed for.
AFAIK, the EuroPlus are made in Ireland. A EuroPlus should also have a modified logic board (a few jumpers change)
If your logic board does not have those changes, it's possible you have a stock II Plus fitted with a EuroPlus lid.
Depends on if the board has enough sockets for 4MB, and how attached you are to that motherboard.
DIP does get rather expensive, and to reach 4MB you're talking about 36 chips.
Assuming the board is fitted with that many sockets, cost of DIP is still considerable.
If you're not emotionally...