Need help determining gold content of/on coin...

[Silver Surfer]

I have 3 1968 Mexico Olympics commemorative coins and need help on one of them. Two are silver and one is gold colored. I spent hours trying to ascertain why one was gold, yet marked with the .720 mark the same as the other two, and found nothing. No info on whether some were plated or clad in gold, or minted in solid gold.
Here is my dilemma. I purchased a gold tester (electronic) awhile back after being fooled by a "gold" necklace I found, and it seems to work properly after testing many gold/non-gold items. I even found that a ring I had bought for my wife years back, although stamped 14k, doesnt even test positive for gold plate.
I tested the coin, and it tests as solid 22K gold. It leaves a strong, solid line on the tester, whereas gold plated stuff leaves a broken line that soon peters out.. I even made several lines using the same spot on the coin to see if it petered out eventually, as I think heavy gold plate would, but the line stays solid. As far as I know, the only way to really know is to cut the coin, but that would then ruin the coin, so I have ruled that out. I also dont want to sell a coin as gold clad and then it turned out to be solid.
Is gold clad thick enough to test as solid gold?
I weighed all three coins on my scale without moving the scale so to ensure consistency, and the following weights were observed..

Silver coin 1- 22.56 g
Silver coin 2- 22.37 g
"Gold" coin - 22.60 g

I would think that a solid gold coin would weigh considerably more than the same coin in silver, and as you can see, the difference is there, but not a lot. That makes me think that the coin is gold clad over silver. That would account for it being slightly heavier.

As always, I know that people on this board know their stuff, and I will get an answer.

Thanks in advance, and HH to all!

SS

 

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[ivan salis]

looking in my world coin book there is no listing of "gold" coins made for the 1968 peroid in mexico -- only silvers -- I think you got a very heavy gold plated silver coin most likely that or a extremely rare mistake -- a gold coin made with a silver coins die -- being no gold coins were being minted in 1968 that I know of the heavy gold plated silver is the best bet. in my veiw.

 

[Silver Surfer]

Have to agree Ivan, that is what I have been thinking.... Gold clad, as I understand it, is like laying gold on top of the other metal and "fusing" it together, whereas plating is electrically done, and only deals with a thin, molecular, exchange of metals. I think it may be clad with gold (as in "gold filled"), but as with you, I can find nothing saying it was ever done. So I have to ask why? Who?
I hope someone that really knows their stuff can come on and say "if it were solid gold, it would weigh xx g, not xx g"... Then I would know for sure.
I guess I should look up what I can that deals with silver weight vs gold weight...
Keep the comments coming though..

SS

 

[ivan salis]

comman sense tells you it would be much heavier -- equal sized gold and silver items--the gold item would be much heavier than the silver one -- the weight is right for a silver item clad with gold or with extra heavy gold plating

 

[Silver Surfer]

Thanks for your ideas and info Ivan.... Just curious, do you think it would be worth much more than the silver ones just for the rarity of it? Like I said, I haven't found any other examples of this coin, gold plated at least...

 

[jdsarasin8194]

well, these are commemeratives from the olympics so, who knows?
nice finds

 

[ivan salis]

normally speaking collector wize --plating ruins the coins "collector" value -- it does however tend increase the appeal of it as a jewelry item * -- which is why some folks plate silver coins --it makes them "appear" to be a much more valuible "gold coin" unless they are very closely inspected by a knowing person.

 

[Silver Surfer]

I will probably sell the three as a group then.... Can anyone tell me what kind of weight difference there would be between a 70% silver coin versus a gold coin of the same size? That would be proof enough that it is plated.

 

[ivan salis]

I do not know the exact differance but it would be very noticible -- since gold is much heavier than silver --size for size .

 

[Letsgethammered]

Consider the Canadian maple bullion issues.These are .9999 pure.Each weigh exactly one ounce.

The gold maple dimensions are 30mm x 2.87mm while the silver maple is 38mm x 2.87.

A considerable difference in size.