I opened up a RRG Hampden 15j 1884 Mermod Jaccard & co. Model 3 lever set stem wind with gold jewel settings the other day and saw this mainspring barrel. I have never seen one like it before. Is there something I should know before I remove it? I am not going to mess with it unless I need to in the future but I don't know what that star wheel is for on the top of the barrel.

Thanks,
Harry

Hi Harry , that is a spring barrel with "stop works " on it , It is used to keep the mainspring at its optimum pressure , by not allowing it to run all the way down . I am having trouble explaining it , maybe some one else could do better. This link will help

https://ihc185.infopop.cc/eve/...741080133#1741080133

Thank you Kevin and thanks for the link. David explained it very well as did you. This one is running so I am not going to mess with it but it looks complete to me but I guess you would have to take the barrel apart to see. It looks to be a high quality 15j movement.

Thanks again Kevin,
Harry

Part of the stop work is missing so it has no effect. That being so, the barrel can be treated like any other.

Thank you John. I will have to try and find a picture so I can see what it used to look like before whatever part is missing was removed.

Harry

I found a picture now that I know what it is called and I see the part that is missing. I have those parts somewhere now I know where it goes as long as they fit.

Thanks for all the help!

Harry