Hi, I bought a Primus 1023 on a flee market in Sweden. In a rather good shape, needle working , pump working, no dents the glas is not broken. And there is a unused glow sock on it. Only thing is the hood, someone painted it silver, I suppose it should have the same green as a 1020? I do not find much information on just the 1023, not on the internet or here on the forum. And I wonder, the small screw between the pump and the tanklock what is the use of it? Ton.
I assume that you mean 1320, and not 1023? 1320 is the alcohol fueled version of 1020. The screw on the tank is just a blanking screw. You could get an optional pressure gauge on some lanterns, and that one was mounted where this screw is. Not sure the 1320 had this kind manometer. I have seen a manometer combined with the filling cap on these.
The 1023 is an indoor lamp that is based on the 1020. It has a different globe cage with no way to attach a handle and the hood is nickel plated brass with no top cap. It is meant to be used with a glass or metal shade. What yours looks like is a 1020 built on a 1023 tank. As you say, the hood has been painted and is most likely green underneath. Probably with a lot of rust. What you have is not unheard of as I have seen a couple of what look like 991 lanterns but have a 992 tank.