The reason there are thick and thin versions of the 1959 medals is because near the end of 1959, Mr. McNamara was told that his medals violated Federal Law because they were the same size as U.S. Half Dollars and could be used as slugs.  To remedy this situation, Mr. McNamara increased the weight of his medals to 262 grains creating the thin (191 grain) and thick versions of the Hawaii and St. Lawrence Seaway Medals.  After 1959, all medals were of the thick variety.

What an interesting concept, slugs that had a higher silver content than US half dollars! ...and by the way, cost more than a standard US half-dollar!

Government gotta protect their rice bowl.  (:

That is hilarious Gary..Mokie these are like our thin/thick Norse medals, kinda..

I'm on a roll like are you really going to plug a cigarette machine with one of these in 1959! Sounds to me like the government had an axe to grind against Mr McNamara.

Just like they do now against Steve Carr and his work. What is this cigarette machine you speak of??Just kidding. I had them in my High School.

You know you're putting out quality stuff when the Treasury department takes an interest in your work. Bet'cha if you put out a cent-sized medal with Mary Lincoln sporting a beard they'd even have an issue with that.

Got to do what you have to do