Never pawn items to gamble - find a bookie who will extend credit against the items you want to pawn.
Pawn shops pay 10-35% of what they can sell something for - a lot of headache holding stuff for 90 days and risking it being stolen. Stuff like tools and electronics are 10% items - gold/silver 35% of melt and guns do well generally.
Guitars used to be a big seller - these days not so much for a variety of reasons. A while back had a friend who scored a dozen Chibsons (cheap Chinese knock off Gibson guitars) - paid like $140 each - a real deal Gibson is between 2-4k new. Anyway - these looked ok from 15 feet away - look up close and know what you’re looking at - you can spot the fakes easily. Went to some of the lowest level pawn shops - dumped them all for $500 each to some sucker who felt he was going to toss onto eBay for $1500-2k and clean up. Eventually they got wise to the scam and he moved to Marketplace and WhatsApp for a while.
But if your pledging collateral - should be no problem getting 75% value in bets. Pure profit to the bookie if you lose and anyone desperate enough to pawn heirloom jewelry or coins is bound to be a long term loser. Interesting discussion, and I agree that you shouldn't use a pawnshop for collateral if your goal is gambling. If you do decide to go this route, you might want to consider alternatives, such as finding bookmakers that may offer more flexible terms, especially if you have valuables to pledge. Instead of using a pawnshop, you might want to consider the platforms I read about at
https://icasinoreviews.co.nz/blog/skycity-online-casino-withdrawal-time/ that offer not only good gaming options, but also reliable information about withdrawals. This will help you avoid the undesirable consequences of quick loans and focus on safe and fun games without risking your valuables. Gambling should be fun, not a financial hassle.