Here is what is stamped on the inside of the rim on my '13 front wheel. No rust ever, and pretty decent for 103 years old too. Manufactured By: W.K. Prudden & Co. Lansing, Mich. Then it has 30 on top, and a 3 under that. Don't recall seeing that before, but the last one it did was over 50 years ago!
My Prudden rears are stamped the same and have the 30 over the 3-1/2 just in front of the name.
Ken in Texas