I have a Fieldscope I from 1981 or shortly thereafter (actually, it is labeled as "Spotting Scope" on the side and instruction manual, but it is the original Fieldscope). It looks similar to the later models. It is of supremely solid construction (has an all-metal exterior; both FSII and FSIII have a rubberized portion on the prism housing for some reason) and has survived all these years, used and abused by others--I'm not the original owner--without a case.
Optics are coated, either fully or nearly so (FS II is almost fully multicoated, FSIII is fully multicoated). Color rendition is very neutral. It is not waterproof but is claimed to be water-resistant (FSII also not waterproof, FSIII is waterproof). Performance-wise I've compared it to many contemporary nonED 60mm scopes and find it to be quite competitive (even against the light). The biggest limitation is that the protective glass in the scope body (that keeps dust from entering when the eyepiece is removed) is very close to the eyepiece, so even though the thread attachment is the same, none of the zoom or wide field (WF) Fieldscope eyepieces (manufactured later, for the FSII and FSIII) except the 24x will fit it (the zooms and the higher power fixed WF eyepieces have built-in Barlows that extend into the scope body a bit). Eyepiece selection is thus limited to the 20x that it came with or my newer 24x WA. The non WF 40x Fieldscope eyepiece is still available (haven't seen the 15x, 30, or 60x non WF for sale in years) but it doesn't have enough eye-relief for me as a glasses wearer. I usually just use the 20x, which is very nice and keep the 24x on my 78mm ED where it functions as a 30x WA.
Really, it's a beautiful and very handy little scope. I don't use a case on it--just have a Bushwacker flip-up cap fitted to the front (there is no sunshade, the FSIII was the first to incorporate one) and a plastic medicine bottle that slides over the eyepiece to cap the other end. I have to admit, if not for the eyepiece limitation, I might have been able to resist getting the 50mm ED (as I did recently), because although the 50ED is lighter, its plastic construction surely isn't nearly as durable, and it really isn't much shorter or compact when packed than the FSI.
--AP