I remember seeing a handguard with an .U. but I don’t remember the other markings. It was either in a book or on an auction sight. I took a quick look through the books I have and the only reference I found was in J. C. Harrisons “The M1icon Carbine III” in it he claims Underwood supplied handguards to Irwin Pederson with a ”.U.” I'm pretty sure the one I am thinking of had the dots even with the bottom of the U like the stamp on Ebay. The on the stock I have with Underwood's rebuild stamps the dots are about even with the top of the radius.

If the fog lifts off the memory and I can come up with something more substantial I will add to this thread.

John