We had someone recently asking about their Vader hilt with "U" stamped on it but with two dots either side. I asked the person to sign up here and share pics and info here. There was also a couple of threads I dug out on RS regarding "U" stamped hilts. I'll try and find them later.
I'd say your "U" lettered saber looks good so far but would be nice to get some more confirmation about others.