Just looked at a couple of Leupold SX-4 spotting scopes in the local Sportsmans Warehouse, and could not find a serial number on them. Does Leupold not put serial numbers on their spotters?

Haven’t look at any of the sx-4 spotters to know for sure but have owns a few leupold spotters for dedicated leave in the truck use and all had serial numbers. A buddy had the cheap Sx-1 and his was printed via what appeared to be a dot matrix printer on the objective barrel.

I have a 15-40x60mm Gold Ring spotter and mine is engraved in the gold ring strip on the objective.

If it's the same coding as rifle scopes, the U at the end represents 2009 which is about right.

Contacted Leupold out of curiosity, their SX-4 spotters are not serialized.