[Erik Latranyi]

Yup, the hammer was internal to the design.

It functioned as a double-action only pistol.

[Mr Rogers]

Looks like a Bodyguard.

https://www.americanrifleman.org/content/this-old-gun-smith-wesson-model-49-bodyguard/

[pingman]

The hammer is only “shrouded” and can be manually cocked.

[HartleyMBaldwin]

It functioned as a double-action only pistol.

Not exactly. There's a little hammer stub at the back of the shroud so that you can cock it and fire it single-action if you want to.