I have a bunch of ps/2 Fujitsu and some more modern ps/2 IBM keyboards which I use a lot of, but for my retro setup I prefer a large 5pin AT PHILIPS keyboard I picked up at a thrift store a while ago. (pic to follow soon).
As for a mouse for retro computing, my Microsoft Cordless Wheel (ball) Mouse with serial connector and PS/2 adaptor is one of the best mice I have ever used because the build quality is amazing (feels nice and heavy and button press is very responsive yet solid) and the mouse itself is the largest one I have ever used and it's very nice when you have (sort of) big hands like mine and it's a true serial mouse (with included adaptor) that's wireless.
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I prefer to use this mouse in my setup, but the only problem is that I can't get it to work with my KVM switch (yet 😀 ). I am going to try another 8 port KVM I have that will hopefully work.
When I get home I will try to post a pic comparing this mouse with a typical "newer" microsoft optical mouse...I wish they made serial compatible optical mice that were this big (and simple)...that would be my dream mouse. I find that there are gaming mice out there that are fairly large as well but they all have cheezy blue led's and the build quality leaves something to be desired.