Allengelhard lists the slightly larger old logo on 10oz PM bars being different - quite similar to my eye https://allengelhard.com/wp-content/uploads/2015/04/pm-bar.jpg Is it the same with the 20ozers? I have a growing collection, and think I have 2 that have a larger stamp, but could just be natural variations I'm not an expert. The 2 on the left (i.e. two top ones in this pic) I reckon are bigger And here is a side by side And just for show - the rarer modern stamp
Most people use xrf - I generally just weigh and compare as I don't think many people would be trying to fake 10oz and 20oz PM bars, and if they did they'd have to be pretty good just to pass the weight/eye test.
I have even found new 10oz PM bars with slightly different shape. I was the one who discovered the different/bigger logo and it is clearly different
Cast Bars Product Code Description Purity % Fine Oz per unit Fabrication Premium Gold Bars A1BD Gold 1oz Bar 99.99 1 $39.00 A1BN Gold 5oz Bar 99.99 5 $150.00 A1BB Gold 10oz Bar 99.99 9.999 $250.00 A1BO Gold 20oz Bar 99.99 19.998 $400.00 A1BA Gold 1KG Bar 99.99 32.148 $600.00 A1BI Gold 50oz Bar 99.99 49.995 $750.00 A1BJ Gold 400oz approx. Bar 99.5+ 400 +/- $2000.00 Silver Bars A2BB Silver 10oz Bar 99.9 10 $39.00 A2BO Silver 20oz Bar 99.9 20 $45.00 A2BA Silver 1KG Bar 99.9 32.151 $60.00 A2BP Silver 100oz Bar 99.9 100 $150.00 A2BL Silver 1000oz approx. Bar 99.9 1000 +/- $1000 *Note that some products may be temporarily unavailable from time to time due to production lead time constraints.* Fabrication used to be much cheaper, how much did it go up by?