If you look at my signature pic I have very similar wheels, mine are apparently bbs rz (apparently bbs made a few different styles of rz) but I dont know for sure. Mine are 15" 4x100. Are your 15" cus they look smaller? might be because the tyres are not low profile.
I think these wheels are standard fitment on some corrado G60's so I hear. Hope it helps
The wheels you both have are from a BMW E30, they come in 14" and 15" - I know this because I also have them

They are def BBS wheels, think your right about 'rz' (never been to sure tho) if you ebay E30 centre caps you will come across a lot of them.
They are also two different types of centre caps, one made from plastic the other metal, tends to be around £17-20 for a metal one.
EDIT: I think you also get push fit and screw fit, think the genuine BMW wheels were all screw fit, have a look to see what you have on yours first