Have a friend that has an upper receiver that was purchased from SAW in the 1980's. It is a shorty and the lower was purchased also in the 1980's and it has a manufactuer name called
Gristmill MFG Co. RosenDale N.Y.
also on receiver is name "Valley Firearms PoughKeepsie N.Y. USA
It has MOD XM177E3 marked on side of receiver.
Has any one heard of this??
Who is manuf??? It is not listed on serial number website...

The mfg is "Gristmill MFG Co." of "RosenDale N.Y.".  They did small runs of AR receivers, and I believe are now out of business.

They produced in small enough quantity to escape the notice of most serial number lists.