Your best bet would be to contact Marksman directly. BTW Beeman airguns owns Marksman. See the link below
The Marksman was made from the mid 70' to sometime in the 80's. Answers has no way of displaying photographs but I did a web search on "Markaman 740 air gun" and found several images of the rifle. It should not be hard to find them. It's a breal barrel rifle.
You can find them at ranges and American guns for sale On Semtemper10 To Nover 19th
I would search the web for "Air gun Repair" and locate a shop near you that can repair it or see the link below for shops that repair air guns.
At it's very best this rifle is worth $18 in Very good condition. It is not worth repairing.
Your best bet is to go on-line and do a search for "Airgun repair" and locate a shop near you for repairs.
go on the computer and scan the words 'marksman air pistol' ...............
The Marksman Repeater is made so poorly that it is not worth repairing. In excellent condition it is worth $15. Broken it is worth nothing. A new model 1010 cost under $20 If you want to pay more than it is worth, look up "Air gun Repair" on the net and find someone near you to rebuild it. No-one seem to have a diagram on the repeater but I did find this on the web. See the attached link below Scroll down to the bottom of the page and you will find photos of how this guy put his back togather.
85 years
No-one seem to have a diagram on the repeater but I did find this on the web. see the link below
Crankshaft Coalition and wiseGEEK provide information and tips on how to rebuild engines. About provides information on how to rebuild motorcycle engines.
Personally you can not rebuild a steering colum you have to find a professional.