i think there's some confusion over numbers of the complete glasses ettinghausen and grabar only suggest one for minden not sure where you got the figure of two from i got one at germanisches nationalmuseum nuremberg from but now i start looking more thoroughly i can't find it anywhere else erdmann says there are two at namur and other sources corroborate that annoyingly i don't have access to jstor so can't check the rest of the articles cited to see if they elaborate also for the fragments where there is more than one fragment it's not made explicit what the minimum number of glasses represented by those fragments is as far as i can see fragments doesn't necessarily different glasses