Ebay Sperry Unisys Boards (leaknoil)

[Jonas Otter]

Some kind of US Military Standard Electronic Module, see

http://www.tpub.com/content/MIL-SPEC/MIL-M/
(the marking M28787 is the MIL-M number)

Referred to here:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.129.4343&rep=rep1&type=pdf

No idea what they are/were used in.

If you Google for M28787 there are dozens of surplus supply outfits
selling these.

/Jonas