The ST-III was strange. They made it for a long time with a lot of changes. The early ones were mostly almost one offs, the latest ones were very similar to the IV. I had a 4x5 that the factory said was made in 1957* and about the only noticeable difference between it and a IV was that it still had the old style lens boards.
Because of that, early models are terribly hard to find parts for or get repaired. If it does not have the international (Graflok) back and the dished front panel, I would avoid it except as a collectors item.
* you will read that they quit making the III in 1956, I have, but in fact the IV was announce at Photokina 1957 and most likely did not hit the streets until 1958. The IV was probably the best selling Super Technika, there seem to be a lot of them out there despite only having been made for 4 years. Although if they had continued using the same naming convention the ones they currently sell would still be IV's as they are less different from a IV than the last III was from the first III.
As to what it is worth, there is a very strange thing about asking such questions of a bunch of folks who would like to have such a camera. If it is a bargain, you can bet it is gone before you get your first answer. Actually, what anything is worth is what YOU are willing to pay for it. There are no fixed prices on collectables there are too many things going on there that have nothing to do with the item itself.
