Got A Tricky One - Industrial Silver Ingots

Just a hunch here, but the remaining metal may be Zinc. That could explain the color. It sounds like some type of brazing alloy. If the remaining five percent is Zinc, the refining cost likely would consume most of the Silver value. You could try a specific gravity test for several samples and compare the results to a calculated range for expected values if the remainder is Zinc, but any variances in the composition and how the alloy could have been mixed make this a bit iffy.

Got APMEX kit. Seems like it's really not geared toward this kind of thing. It includes and envelope, but clearly intent is to just send coins or jewelry, not bulk things like this. The MO is "send it to us and we'll give you an estimate - if you like it we'll pay you, otherwise we'll return it". Says they'll buy jewelry, silverware, dental gold, or gold or silver decor; this doesn't really fit into any of those. So - thinking no on APMEX.

I did talk with the owner of this place though:

https://mbpreciousmetals.com/

Anyone deal with them before?

They seem good - been around for a long time, and the guy I talked with knew his stuff. He's planning to meet with me at some point; he'll give deposit and get the metals, then pay rest after melt and full eval. Said he generally pays around 80% of spot, which is about what I would expect.

They specialize in recycling dental metals around the region; can do other things like this as well, and was fine doing ad-hoc buy (vs other place where I'd need to create an account as an official seller and such).

Edit: I posted a link to the wrong place a minute ago; corrected.