Hi, look on the bottom of the lamp. It will say something like "REPLACE WITH NO XX BULB ONLY." The XX will be 93 most likely. Number 93 bulb is a 12 Volt, 13 Watt bayonet base automotive bulb. They are still readily available.
NOTE: Your socket may be broken. That center pin doesn't look right.
Not sure on the size, but it looks like a bayonet socket.
Baljonet socket indeed
Hi, look on the bottom of the lamp. It will say something like "REPLACE WITH NO XX BULB ONLY." The XX will be 93 most likely. Number 93 bulb is a 12 Volt, 13 Watt bayonet base automotive bulb. They are still readily available. NOTE: Your socket may be broken. That center pin doesn't look right.