Thank you all for looking so carefully at the evidence.

The * over U is also on the flat part of the action that mates with this flat part of the barrels (is that the water table?). Inspection with the naked eye of the character in question is much more lower case alpha than small x: on the left barrel (in the picture) there's a curved portion of the character in the 7 o'clock position that looks like the left side of an alpha.

This makes for an interesting question about production date. Is there any question about the numbering system and the year associated with 253xx? How about style clues?