It's definitely a conventional spray head. But the way the trigger is configured and it being made out of what looks like brass it could be 50-60 years old or more. The last time I saw one with a similar trigger made out of brass it had gone out of production in 1949. Does it have any company name like Binks or Devilbiss on it? Anything that looks like a part number? If it doesn't it is probably a cheap knockoff but hard to tell. If it is that old you would probably need to re-pack it because the o-rings are probably shot. There wouldn't be any re-pack kit available so you would have to match up the o-ring sizes. The hard part to replace would be the packing or packings where the needle goes through the body under what was a knurled compression nut. That would probably be a unique part to this gun and would be hard to find. I also doubt that you would be able to find replacement needles, nozzles, and air caps for it but it is hard to say with out knowing the brand. ( I managed a Sherworks department for 9 years. This kind of spray equipment was at least 70% of what we worked on and sold.)
The fluid and air fittings should be the same as today's standard sizes, as they have been standardized since around the late 30's.