Help decoding seatbelt date code

[Carl Spangler]

Greets

Can someone help me decode the following seatbelt date code from my 1971 C10: 52K70. Looks like 1970 but is the 52 the week # and what is the K?

I'm trying to narrow down the build month of my truck. There are a couple threads listing some date codes and S/N's. Unfortunately, the corner of the blue door decal on my truck is damaged. I looked behind the seat but the build sheet isn't there.

From previous 67-72chevytrucks threads:

Z602191 8/70

Z622515 my truck looks like it could be Dec 1970

Z641136 4/71