Gold tester

[Nomiracle]

Hello this is my first post to this forum so please excuse me if I don't do it right but I will try to keep within guidelines.

I wonder if anybody can help me I recently purchased a gold testing machine which appears to be circa 1970 ish because I have some gold that I would like to test to see if it's genuine.
I've tried to attach pictures but it appears that they're all too big to upload despite my trying to make them smaller but if anybody is interested I could send them via email. The machine doesn't work and won't go past the second screen whereby it asks me to use the probe which is the one picture that I have sent although you can't see the whole machine.
I have a general idea of electronics but I'm far from being an expert and and the 'pen' part of the machine puzzles me because there doesn't appear to be any metal tip protruding from the end of it despite there being a hole so I wonder if when I put some gold into the crocodile clip and try to test it with the pen this is why it's not coming up with any further reading. I've done some research on this particular machine and it appears that it's the only one in existence! Wonder if it was a prototype used for a sales team planning on selling it eventually? Any help with this would be gratefully appreciated.
Thanks in advance



[Mod note- resize and rotate image ]

 

[PETERDECO]

Welcome to the forum. If you suspect that machine is the only one in existence, I wouldn't trust it. Do what jewelers do:

Test With Nitric Acid
Make a mark deep enough to scratch through the top layer of gold. Carefully apply a drop of nitric acid to the mark, and determine if the mark turns green or milky. There will be no reaction if the jewelry is either gold or mostly gold.

 

[Nomiracle]

Thank you I appreciate your reply, I've purchased an acid test kit but was hoping to sort this kit as usually the more modern ones ( which basically work on the same 'ohms law' principle) are apparently very precise and so I thought that perhaps I could make this one somewhere near as precise for a fraction of what the more modern ones cost and and less messy! I've taken the probe apart but it's very confusing to look at I'm not sure if it's that that needs attending to.

 

[Harald Kapp]

it appears that they're all too big to upload

< 300 kB works well.