armrest, 450sel
 

my 74 450sel had an armrest in the trunk when i bought it. the armrest has a post on it and there is a corresponding bracket with a hole in it on the passenger seat. it appears to be a press in fit without any fasteners. anyone have experience with this?

Typically the MB armrests secure to the driver's seat with 2 hex head bolts. A plastic cover snaps in place to hide the bolt heads.

my 74 280 has its armrest on the passenger seat same as the 450sel

Regardless, the armrest should fasten to the passenger's seat with 2 hex head bolts. Check your 1974 280 and see how the armrest is fastened.