How old is this Monkey Wards drill?

[Mel Larsen]

Another of my drill collection.  Any way to tell how old it is?  I don't think the chuck it original and what caught my eye is the little tin trigger.
Mel

[Bill Houghton]

It looks like the Portable Electric Tools (PET) drill I sold a while back.  No photo of mine, I'm afraid.  The chuck does NOT look original; certainly not like the PET drill chuck, which looked more consistent with the design.

I believe it's from the 1950s.