The single ended projector lamp is usually a capsule style with a ceramic base and should look like the picture – although the base can look slightly different depending on which one it is.
There are many many combinations of wattage, voltage and base!
If it connects with two pins it is the distance apart which may help determine the exact lamp you need (eg a GY9.5 mean 9.5mm apart)
Projector lamps have short but glorious life so it is worth keeping a spare in the cupboard.
If you know or can read the code number of the lamp this makes identification much easier!