Polo Ralph Lauren jacket size label - from the Made in USA era

[pwc008]

I just bought from ebay a what I thought was a PRL sport coat (it is USA made), but I think it's an orphaned suit jacket. It was less than $45.00 and is in mint condition so it's no big deal, but the inside pocket label says: 46/40 REG. Other PRL jackets I have acquired from the USA made PRL era just say 46 REG or 44 REG. (I wear both.)

Thoughts anyone?