The seat and inner post look like tricycle parts.
“MONARK” was a bicycle manufacturer and wholesaler (as well as a bike retailer).
Earlier they were into automobile batteries.
All of the items that are original to the bike could be said to be “MONARK” parts and accessories; the springer is most recognizable. The paisley chain ring is also recognizable, (but similar to another).
Frame takes a 3/4in seat post.. and the one thats on there fits perfect. .All my other posts measure in at 5/8ths / 11/16ths and they are too small.
If it is stock... Do you have any pics of through bolt and wedge ??
I understand the concept , but it doesnt seem like what i have.
Thanks for the info !!
13/16" (0.81" or 20.6mm) seat posts are common; some transition to a reduced 5/8" for seats with clamps that are 5/8".
7/8, 3/4, 29/32, 5/8, 1" are also common.
If 1/16" tubing is used with a 5/8" outside diameter post, a 1/2" inside diameter might result.
One might find and fit a 1/2" bar into a 13/16" post reduced to 5/8" at top, in a telescoping manner.
Fairly small cycles might use small (1/2") solid bar seat posts. Larger bikes use stronger hardware.