3 digitit numbers refer to metal purity so it is 82.5%.
If you have an acid test kit you can tell if it is silver, gold or platinum. Common silver marks are 925. For the jems. Quick huff test, huff on them and if there is any fogging they could be CZ's, No fogging is likely a diamond.
With a loupe look at the facets and if there is any rainbow (refractions of light) it is a man made stone. Just reflections it could be a real diamond.
Lastly natural stones have inclusions (bits of dirt inside) where lab grown gems have no inclusions.
For quality of diamonds if your really interested in selling it might be worth spending some money for certification. That is when they are professionally compared to sets. I think many jewelers charge around $100 ea.

That is a pretty nice looking ring. Congrats.