Thanks Luker,
Yes it is a 6 speed I should have mentioned that, There are two numbers stamped into the Sachs/Huret derailler of 14 and 28. The 14 may be the first one as the second is 17. I'll check it further this evening when I am home. I can always do as you suggest and just count them all, but I thought there might be some reference numbers to find.