Help ID this second stage?

[tbone1004]

View attachment 194900View attachment 194901

Pulled these from a craigslist ad and had to post because I've never seen that first stage before. It looks like a cross between a Jetstream and Cyklon from Poseidon, but seller says it is Sherwood. Any help with id?

 

[claymore]

The attachments come up as invalid. I think I remember reading that Sherwood used a Poseidon second on some of their regs at one time. I do not know which second or when it was.

 

[tbone1004]

strange since it looks like a cyklon head on a modified jetstream body

 

[Fishpie]

Submarex Atmos