Thanks for the kind offer,if Stefan cant help I may just take you up on it.If you want to send it to me I will always try and get it out for you. I work on clocks so have a lot of small tools that might do the job. Won't charge you a bean except I'd ask you pay the postage. That said you might have trouble getting a new stem too! As John says give Seiko superman Stefan aka seikochrono a shout as he's your best bet for NOS.
How do you mean 2 parter ? I thought, well i know it is a one piece stem with a gear and spring fitted.If your hunt for a genuine Seiko OEM fails, I have it in genuine vintage NOS aftermarket in both silver and gilt. Cheap, as always.
No luck on the stem though, this one takes a 2-parter.