I would leave it alone, original, and in the envelope, and have a reproduction one made.
The below person does the 67-72s, I do not know about squares but someone must do them.
http://outintheshop.com/2.html
I realize that people frequently offer alternatives to what the question is about as opposed to an actual answer and that is what I have done, it can be annoying. So I would say that if you really want to restore your original SPID I would take it to a conservator. If you cannot find one, most frames shops could provide you with a contact.