the arms clip onto the complete shaft in Daves first pic
when they fall off they can come off with the splined end of the shaft still in the arm
i.e the bigger round splined chunk in daves third pic is still in the end of the wiper
hence you will need to take off the other one to see if you need a wiper or a wiper and wiper pivot.
he wasn't just posting up nice pics for the sake of it
or
If you can push the wiper pivot back into the scuttle then the end has come off and is lost with the wiper
the arms are US model specific (aussie cars all used the same kind)
the pivots are 1960s/70s chrysler model specific (aussie cars all used the same kind)
the wiper heads use a world wide universal style clip and are usually replacable with any old 70s one try hillman humber etc
the blades are just any old rubbber.
so if the end of the arm looks like it has no splines it could be because it took the end of the pivot with it.
lever the clip on the arm up and pull out the splined bit
stick it back on the pivot shaft with super glue
have toyed with a circlip or a grubscrew idea before but never got round to doing it.
you will have to take out the ashtray and stuff and get something wedged against the back of the wiper pivot unde the dash while you welly the end back on. I find the actual ashtry fits nicely between dash back and wiper pivot
but it tends to ruin the paint.
i now use dental floss tied to the vent in the front scuttle and to the wiper to make sure i don't loose mine.
hasn't come off in two years
Dave