Congrats Darko. My vote goes for opening and displaying it.
As for your question. I looked at some of my SJs and the patent number disappears at some point. I've seen it on SJs as late as N code, then the SJs I have with later stamps AD, DD, etc. do not have the patent number. The patent number listed 3,538,906 is for the leg socket design so I'm not sure why it was even on SJs except for ease of manufacturing.
A question. Should EO code webers have a patent on the vent? I don't recall seeing it on the redhead I gave my friend, or the Packers SJ I sold to a workmate.