One thing no-one touched on is matching a pump to a vehicle. A T pump would look ok with an 80,s car a visible would not. So people that work with and display a certain vehicle usually want the pump era to match the cars. A visible just dont look right with a motorcycle, but looks pretty good with a model A. Part of the reason I like some of the pre-visibles without doors is I like early bikes. A handcrank pump looks great with a teens bike. Also what I like about the handcranks is they are very mechanical and nothing is hidden on them, you can look at it for a minute and figure out how it works. And handcranks are easy to display with a bike at a show, make a wooden box and just carry it.
However I dont recall ever seeing one in use(but still find them interesting and desireable), but did find one 1/4 mile from where I lived. Got used to fill a school bus.
Desireability is a great factor in building appreciating value in a collectible. Some things were just so cool to look at and touch that people have to collect them, and they will remain popular for a long time.
Biggest factor in keeping stuff for speculative future value is storage. Usually costs one way or another, and if things change and you lose storage it can be a big problem..hard to throw stuff out especially after moving it a few times, taking care of it and having paid cash for it.
Interesting subject...dodogas
