The big open shape of the teardrop
the single rivet attachments
and the single bolts attaching to the fender
Schwinn rivet heads are smaller that others and almost hemispherical
Other makes are pretty flat
(with the exception of rivets on later 30's Colsons with flat braces )
In other makes where the tab takes 2 braces,
one brace has one rivet so it can pivot while the other has 2 so it is fixed.
Also nearly all other makes are attached to the fender with 2 rivets (or bolts).
Schwinn uses the same single rivet axle tabs on flat braces through about 1937
but the fender attachment changes to 2 rivets when the fenders change from flat/gutter to round
There is a similar brace used on early Snyder-mades with gutter fenders
but the teardrop window is smaller, the single rivet heads on the axle tab are bigger and flatter,
and it has double rivets where it attaches to the fender