new:
has various security features including the watermark, copper (or something) wire inside, etc.
old:
has very few security features if any
there were several iterations between the two
also,
quite rare, often kept for superstitious or sentimental value
clerks from other countries (here, stereotypically, arabs) sometimes don't realize they are an actual thing
$50 bills are fairly uncommon too unless you are in neighborhoods/areas where people usually cash their paychecks
if not from a check cashing store, here $100 bills are typically from the illicit drug business
and no doubt the two circulate frequently between
otherwise it's almost all $20 aka the "yuppie food stamp" gotten from ATMs
in yuppier parts of town a $100 bill is actually
déclassé as it is suggestive of a lower class person who lacking a bank account cashes their checks; either that, or a drug dealer, or someone trying to impress strippers or whatever
actually in these parts of town paying cash is
déclassé
i once saw a bar that said no cash accepted
a fucking bar
i'm not quite sure who the fuck would such a tend that bar
they probably also have the little meters in the bottles
but i digress