Where Can I Find A Replacement for This Bulb?

Long story, but a relative who lives in a very remote area mailed me a burnt-out light bulb to see I I can find a replacement. There aren’t many markings on the bulb to help narrow the search—just “75W 120V Bulbrite.” Here’s a (blurry) photo. Can anyone help me out?

What is it for? What are the dimensions? That looks like a bayonet socket but it is not very clear.

Looks like a BA15D style.

I think the Wulff has nailed it.

Now we have to guess what it is for:D
My guess is a low powered projector (slide projector)??

I don’t know what it’s for, but thanks for finding it.