Identify the mystery fish

At Cryptomundo, Loren Coleman asks if anyone can identify this mystery fish found on an old postcard? (Please don't email your responses to me. Instead, post them in the Cryptomundo comments.)

 Cryptomundo Cryptids

From the blog:

The men in the picture look like military servicemen. The surroundings look like this photograph was taken on a beach or island. The fish appears to be about six feet long (notice the yard or meter stick lying next to it). But where are the fins on this cryptid (or even a tail)? What is it?

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