Correct dates for fender mounted First Aid kits?

[motorman]

I've seen variations of the fender mounted First Aid kit, and am trying to understand when changes were made to it's appearance. I have factory literature from the late 1920's and early 30's that show a kit bearing a cross within a circle on the lid. Later kits seem to have the words "First Aid" within a circle embossed on the lid. The latch also seems to have changed from a wire hinged latch to one made of spring steel. I don't have sufficient books to track when the changes were made, and am wondering specifically which kit would be correct for 1938?

Thanks for any help.

Paul