I can't picture exactly what is bent, Tom, but check this out:
http://www.micro-tools.com/Merchant2/text-lens.htm
(one of my bookmarks)
Hope this helps,
john

Rodenstock service in the U.S. is:

Marflex

973 808-9626.
Have you asked them or the service center in your country?

There is a special tool for straightening dented lens flanges.  I'm
surprised the repair shop doesn't have one.  Try a store that trades in
used gear - they have a definite need for the tool.

It is also possible to gently pound the dent out with a half-circle cradle
cut in a block of wood and a similarly radiused end of an 8" length of 1x2.  
Place the lens rim in the cradle and the 1x2 inside the rim and pound gently
on the stick.  I have not tried this method, use at your own risk.  
OTOH, pounding metal to shape against a buck is good enough for Muliner
Park Ward and Aston Martin - it should be good enough for a Sironar.  
You may want to use hardwood for the 1x2 (or whatever size lurks in
the wood scrap box).

The tool you probably need is this:
http://www.micro-tools.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=MT&Prod
uct_Code=LV1  but I'd suggest to just leave it alone.

Guillermo

 There are some good shops who can do this sort of work,
Steve Grimes shop at http://www.skgrimes.com  is one of the
best. However, for this lens I agree with Bob Salomon that
the best thing is to get it to Rodenstock's service
deptartment. They will probably replace rather than just
straighten the dented part and check to see that no other
damage was done. In the U.S. Rodenstock uses Marflex, in New
Jersey. They are very reliable and do good work.

Martin W. Arndt

Marflex Service Corporation
PO Box 633,
16 Chapin Road, Unit 906
Pine Brook, NJ 07058

973 808-9626 Voice Mail
973 808-1706 Fax
Marflex@aol.com

Have you called S.K.Grimes??