I have a gold coin that was soldered to a pin and still has some solder on it.

It’s .900 fine gold and .100 copper

I don’t wanna buy a soldering iron…is there any way I can do it at home? Like put it in my oven or something? What temperature will it not melt the gold but melt the solder?

please tell me the correct method of finding the gold contents in ancient coins by using chemicals (which chemicals its ratio) and what kind of reactions will be found, if there is any percentage of gold contents?

I would like toknow how much of other metals are alloyed with gold to make up 9ct gold.

Particularly, how much silver is contaned within a 9ct gold item
Maybe I should have been more specific - what is the typical make up of the 62.5% of other materials. Especially, how much silver?