Impossible to answer without knowing who made it.
AFAIK, Colt never made a single shot pistol
Impossible to answer without the serial number.
50 or so
60's or so
Check the frame, barrel, butt and under the grips
50 USD
10-100 USD or so
Impossible to answer without the serial number.
No serial number provide; 50-850 USD
take out the screw @ the bottom of the handle take handle off serial # is on left side
Buy some books that deal with the type you have.
'K' prefix to serial number indicates 1950.