Need help with a rocket motor ID

While playing "Stump the Bland," "Dave Kearton" wrote:

I've just received a few pics of a small rocket motor, from a friend of
mine.

It's about 2Kg and about 45cm long with a 10cm wide nozzle. It's a
liquid fuel motor and doesn't look like it has any electrical connections.

We're all guessing it could be some form of reaction nozzle for (maybe) a
Gemini or Apollo capsule.

It doesn't look like a Gemini or Apollo article. They had ablative
nozzle linings and assorted electrical components attached to the
top of the unit. The spiral exterior of the casing suggests that this
rocket uses a regenerative cooling system, which I don't think
appeared on Gemini or Apollo.

My best guess is that an amateur rocketeer built it. Failing that, it
*might* be a secondary propulsion motor from an Agena upper stage
or--remotely--a midcourse correction motor from a Ranger/Mariner
test article.

(I'd suggest asking Henry Spencer on sci.space.history, but
jeeze, who wants to despoil ssh with something on-topic?)

--Bill Thompson