With the screws at the top and bottom at rear of reciever it is a boxlock with safety sears,(double sears), this feature is only found on the higher grade European and British boxlocks, There is not much literature around on Simson grades, to me it is comparable to a model XVII or XVIII Sauer. FWIW

Pete, the guy has been on Gunbroker for 5 years with 136 transactions and has a 100% positive feedback. I don't know him but how much history do you want?