Was the Pawn Shop lying regarding the silver I tried to sell?

You got more than one opinion, right?  

there are solid ways to tell the difference

https://soqofficial.com/how-to-tell-the-difference...

I've been in a pawn shop, got offered a rubbish price, also heard other people questioning them about low offers, then walked up the road and got a better price. I heard them complaining that things had either no hallmark or the wrong hallmark and then another one up the road won't say anything and will pay fairly. I think it is all to do with their budgets as well as what your stuff is worth and they fib rather than admit they need to keep their spending down, another one up the road might have a bigger budget. They also have to weigh up the chances of a lot of people not coming back for their items, they might have to sell it and lose some of the profit they would have got had you redeemed the pledge because you are within your rights to let them keep the item instead of buying it back.

Take it to a jeweler and pay for a professional estimate of the value.  When my grandmother died, she left a ton of jewelry. Most of it was trinkets that had no value. But a few items were valuable.

Yeah, it's possible. Take it to a reputable jeweler.