I have a 1983 Case 21051 LSSP with a worked blade and backspring. It belonged to my girlfriend's late husband and I found ti when we were cleaning the garage a year or so ago, so I don't really know the history. It was in rough shape, cleaned it up as best I could. I assumed the worked blade and backspring were done after purchase, but I've recently seen a couple of Case offerings with a worked blade and backspring. One of them said they hadn't seen a Case with a worked backspring for 30 years or more, so I'm wondering if mine could have been done at the factory? Any help would be appreciated. I don't see an option to attach pics or I would, but would gladly email to anyone interested.