This Roosvelt-Quezon coin was part of the Commonwealth commemorative set of Philippines in 1936. Many of them were part of the sunk Manila Bay Treasure (*)
This one has signs of corrosion which may be evidence of sea salvage. Weight: 18.3 gs.
Diammeter: 35 mm
Thicknes: 2.3 mmSG: 10.1
The following information is from Krause Catalog and Numista:
Catalog: KM#177Weight: 20 gs
Composition: 0.900 Silver .5787 Oz. (actually is 0.800
A specific gravity test 10.1 indicates the silver content is close to 0.750. At this point, the weight loss (1,7gs) and SG difference made me doubt about the authenticity.
Can the corrosion explain the weight loss?
A more detailed look gave me the answer, this coin had been pierced and repaired !
Someone has filled the hole and repaired the date, so a restoration with bad quality silver and the corrosion would account the weight loss and SG
Despite the fact that it is in very poor condition, it is a coin with history.
(*) Here is an interesting article about the Manila Bay Treasure:http://corregidor.org/chs_trident/s...bbell_01.htm