Mystery ICs MM5208N-S - Phil is right, 5280, not 5208!

[yorkshire_spam]

I'm starting to unpack all my tech gear and working towards setting up a work bench at the new house (just over 2 years since we moved!)

I've just pulled 2 tubes of ICs out of a box and can't figure out what they are or what I bought them for.

They are NOS National Semiconductor tubes, but the chips are labelled MM5208N-5

A quick google doesn't reveal anything, I think they are RAM of some sort, I have a vague memory of buying some obscure RAMs at some point in the past for something.
They are also rather oddly 0.4" width packages.

Any ideas?

 

[philmurr]

Are you sure it's not MM5280 - RAM as used in SI?

 

[yorkshire_spam]

Are you sure it's not MM5280 - RAM as used in SI?

100% right - my dyslexic eyes strike again - thanks!

Next question is why the hell I bought them since I don't have and SI. I wonder if they are used in any of the early Universal boards I was working on a while back? (Cosmic Monsters, Magic Spot, Zero Hour etc.)