Geiger counter from the 50s

Some time ago I managed to get my hands on an old geiger counter. For no reason, really, I just happen to like vintage tech stuff like this. Although this unit had been modified by someone at some point in the most unpleasant fashion.

The manufacturer is Atomic Research Corporation, and readout says "Model 521" on it. I can't find any absolutely certain information about this (the 521 models I see in net are slightly different, with hand-held radiation sensor; this one has the sensor fixed at the bottom), but so far the best guess places manufacturing date to mid-50s.

Does it work? I don't know. It takes few C-size (I think; might be D-size too) batteries which are no problem, but it additionally needs two 65-volt batteries of type I've never seen that - really - aren't exactly commonly available these days. This is where the modification done by someone comes in play; they attached a box full of 9v batteries in series to generate the high voltage needed by tubes. I consider that modification nothing but crude and vulgar and completely out of spirit of this vintage design and immediately removed it, without even testing if this thing works first.

 I've been thinking about building a boost or flyback transformer to boost lower voltage to more suitable levels, but I don't really have experience building such things (at this high boost factor, I've done boost converters with voltage factor of about 2 before) and so far all my attempts have been miserable failures.

Here is the insides. The large open area is for two 65v-batteries and on right you can see slots for two smaller batteries. Electronics on top is constructed in a fashion fairly typical of the era; everything just wired directly together. Not really most elegant or easiest to work with, but gets the job done. This isn't nuclear scien... oh, wait, it kinda is. Nevermind. Not complicated science though.

The sensing element (I think there is more accurate name for it but I'm too lazy to check now) is fixed on bottom, and there are few openings in the case for it. The crudely cut slots you can see there are for the wires to the battery box attachment. Ugly, ugly.

It even comes with full schematics! Unfortunately they are glued inside of the outer cover and have been somewhat destroyed by repeated removals and insertions of (fairly tight-fitting) insides so I can't get much better picture of them than this. Not very complicated thing as you can see. Unfortunately I have absolutely no knowledge about tubes and their operation so I can't even try to decipher how this is supposed to work. Maybe when (okay: if) I ever get my boost converted design working properly I can try to figure out more about the operation by trial and error, but for now it has to wait, just sitting there on my shelf on display.