I have a Remington Model 81, (.35 Rem) in exceptionally good (original) condition. It has two date codes stamped on the barrel shank area. One is for May 1946 and one is for October 1947.

What does this mean? Part of the gun was manufactured in 1946 but it was assembled in 1947?

These are Patent dates. Each indicates when a particular unique feature of that arm was recorded.

b#, I don't think these are patent dates. If they were patent dates they wouldn't be in "code" like Remington does. The codes put on by Remington from 1921 to 1972 indicate month and year of manufacture.

http://www.remingtonsociety.com/questions/BLACKPOWDERX.htm

My particular rifle was made in the (civilian) manufacturing start-up years right after WWII and it has two such dates.