Model: Spotron Professional
Price (new): $99.95
Cell type: CdS
Measure type: Spot
Batteries (orig): one 1.35v Mercury (RM-450R) and one 22.5v Eveready 505
This bears a very strong resemblance to my Pentax 3/21; so much so that I think Mekano made it for Pentax. Camera makers often buy things (like accessories) from 3rd parties and brand them as their own. I think this Spotron is a later version of that meter, but that's just my opinion.
Regardless, the similarities are striking. It's a similar size, though the case is metal and a lot heavier. Like the Pentax, it uses two circuits and two batteries: a little 1.35v for bright light, and a beefier 22.5v kicks in for low light. They each have a lens on front which mimics a camera lens: it can't be focused but it does have a screw thread on front for filters or a shade. On both meters, the lens collar acts as the calculator.
The differences are small but numerous. This picks out a 2° spot in a 19° field. The viewfinder angle is now horizontal instead of vertical, so you use it at eye level instead of chest-level, and the image is oriented correctly. There's a battery-check function. The neck-strap lugs have been replaced by a threaded socket so you can attach it to a tripod or a pistol-grip. There's a main battery ON/OFF switch which turns the high-level meter on and leaves it on (so you have to remember to turn it off yourself), and the plunger button on the front only runs the low-light boost. Best of all, the battery chamber is now accessed by removing a single thumb-screw, rather than by removing four tiny jeweler's screws.
There are two serious shortfalls: one is that it takes two oddball batteries. Like the Pentax, you can still get the big Everready 505, but the 1.35v Mercury has no proper replacement. You either need to buy one of those $40 battery converters, try an equivalent Wein cell, or get it upgraded and recalibrated to run on a modern 1.5v cell (good luck with that).
The other problem is that it's very heavy. It's not the sort of thing you would want to hang around your neck or even drop in a coat pocket. But if you're carrying a camera bag or case, it's much more reasonable.
The only thing that this thing really needs is a Zone System ring on the calculator.