I'm a little bit late for this post.....
I have very good friends who hand built in they garage real CNC router. And they use it for engraving.
(for Russian lovers could be interesting they web side:
http://www.redstarrc.com/main.html)They never did engraving on cameras yet, but they are willing to try. The advantages are they are local (to me:), from Baltimore(US) and that we can supply individual CAD or COBALT drawing for each camera. Not only different models they can work on, but even personal names or slogans can be engraved. Quantity also not much matter price vice. The disadvantages are that they do not work on cameras or painting. They only can make engravings. We have to send exact drawings in requested format and camera's parts what have to be engraved. We have to put this parts back ourselves. But they should be way less expensive then $150/camera (115E).
Considering what camera to use, I think that Zorki 4 is a great camera, but from historical view it's not first or last rangefinder produced by USSR (like FED), and it's not the most beloved camera like Zenit E or Smena 8. And it's not unique Russian design like Start or Droug. And it's not the cheapest or more available on the market today. By my humble opinion FED 5 could be a better choice. It has historic name, it was last produced rangefinder in USSR, it has all the fixtures what Zorki 4K has, it has as much engraving space, it easy to find, it cheep, it available in black and chrome, FED 5 are pretty fresh, some can be found brand new in a box (which also can be customized), no scratches or damages and no need to wait for SLA. And what is important to me I will not blame myself thinking that I forever kill such historic camera like FED 1 or Zorki 1 by repainting and re engraving it.
But it's only my modest opinion.