I have never seen a state inspection sticker like this before... it's a recreation of a legit window sticker for 1944 passenger cars,

and it's a reminder that there are some really rare things about cars that are only ever going to be seen by either going to see a LOT of car shows, or looking through a LOT of car enthusiast websites like mine, where we find the stuff so you don't have too! 

here's a legit one still attached to a windshield of a 25 Dodge 

https://www.oldcarsweekly.com/features/car-week-1925-dodge-brothers-roadster

you can buy your own at https://coupecustoms.com/product/1944-california-registration-decal/

Decalcomania is the process of transferring pictures or designs from specially prepared paper to glass, ceramic, metal, or other material. 

The American Decalcomania Company was a major decalcomania company in the early twentieth century in the United States. They made these window decals, and the WW2 gas ration decals