I have completed a review of the DP-5B geiger counter sold here on SAS. Vladimir kindly sent me a replacement for the previous one (which had a dead microammeter) and here's the review.
http://neozap.com/Rad/DP5Bgeigerreview.htmIncluded in the review are basic instructions for making battery adapters that allow you to use AA batteries in the DP-5B without bending contacts or modifying anything (so you can keep it as original as possible!).
Happy to answer any questions about the counter, I have more or less worked it out inside and out having disassembled one so let me know if I can help.