"I have a pin/pendant that was my grandmother's. I know it dates pre-1960's, but that is the best I can do on the date. I was told it is platinum by my father. The only marks on this piece is the #962 stamped in two places on the back. I have attached photo. I have looked everywhere and can not find that number connected to any metal. It is definitely not silver. No tarnish in the 20+ years I have had it. No reaction to magnet. Any ideas?"
Elizabeth, i would be interested to know if the clear stones peeping though are diamonds or synthetic stones? If the stones are diamonds I would lean towards the metal being platinum despite the uncommon #962 mark.
Platinum is normally marked:
Jewelry that contains at least 950 parts per thousand of pure platinum may be marked or described as "Platinum" Jewelry that contains 850, 900 or 950 parts per thousand of pure platinum may be marked "Plat" or "Pt" if a number is used in front of the term to disclose the amount of pure platinum in the mix, such as "850 Plat" or "850 Pt", or "950 Plat" or "950 Pt"
In regards the "normal" marks for platinum as above, there are uncommon marks on metals. Rarely you may see something different. But uncommon marks on metals are out there. The odd ones can be easily be calculated using following... for example,
1 karat gold is 1 part in 24 gold. So for instance 22ct or 22K is 22 parts in 24 of pure gold or 22/24ths or if you multiply 22/24 X 1000 you get 916 (916 parts per 1000) or 91.6% gold.
If you see a number, for example 625, divide it by 1000 and multiply by 24, it will give you the carat. 625 / 1000 x 24 = 15ct.
Platinum is a silver metal with a slight greyish caste, and apart from the obvious, your local jeweller testing the metal, or testing the metal with digital metal testing equipment you can use at home, the WEIGHT of the metal is a good indication.
A quick and very approximate test you can perform to check the genuineness of platinum is to measure the dimensions of the piece in centimetres. Multiply together to give the volume.
Multiply the volume by the density of platinum, 21.45 gm/cc.
This will give you the theoretical weight that the piece should be if it is really platinum. If the actual weight is less than 85% of theoretical it is probable that it is not platinum.
