C Merit Badges are not much of a deviance from the Type B
badges, however they do seem to have a composite coating to
help stiffen them a bit.
Type C Merit Badges were introduced around 1936 and were
produced through 1942, except for the four blue Air Scout merit
badges, which were produced through 1946. Type C crimp is about
1/8 of an inch from the embroidered ring of the badge. The size
of Type C merit badges are 1-1/2 inches in diameter; give or
take a fraction either way.
Type C merit badges have their own set of variations, but not
consistent for every badge, while others have all of the
identified variations. Black and brown thread is used in
place of each other for some badges, and the thread itself
varies between silk and cotton; some badges being done in both.