I would not use true-oil, it is not an oil finish. Try raw linseed oil, a tooth brush and maybe some 0000 steel wool. Be gentle. You might read this thread first:

https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=351571&page=3

Oh, and some pics of the gun? We all like seeing 100 year old English sidelocks.


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