Golfing center of tee marker value?

[Dirty Digger Doug]

Does anyone know the value of these brass, GAM center of the tee, USGA markers? I gave been unable to find any information on them.

 

[Mackaydon]

Google Search

www.google.com

Don.....

 

[Dirty Digger Doug]

Thanks Don. I was able to find all kinds of stuff about the GAM but I am asking about the value of the marker. There seems to be no history of the markers, what years they were used or their value.