The problem is, other than me, nobody else really collects them. There are overlaps though. Most metal squirt guns are dirt cheap; however, if it's also a space gun then the price immediately skyrockets! (pun intended)
At some point, I do hope to take good pictures of the entire collection and put together a picture book.
Some years back, had the collection displayed in the front windows of a local shop. It was the only opportunity I've ever had of seeing the entire collection at one time. Had lots of fun talking to folks who showed interest. My opening line was usually, "It's the World's Largest Collection of Metal Squirt Guns." It was fun to talk to people about, what everyone agrees is, a very interesting collection.
On a few days, I also brought some metal squirt guns along and have squirt gun fights outside the store. These, of course, were old school squirt gun fights, since you only got one shot per fill up!
Here's a video:https://www.youtube.com/watch?v=dvX1ETJHqwk