These were designed to screw the stem into the pie, and had slip fitting built into the stem. If the stem didn't line up squarely with with pipe, you could keep turning the stem clockwise until everything was inline.
The Adjustomatic models were manufactured (I believe) in the 50's and 60's, and are so named because you are able to adjust the pitch of the stem without over-turning the stinger in the threaded mortise. The Viscount line started around 1957, and was considered to be one of the higher-end pipes in the Grabow lineup (Eldorado being higher grade), based on grain characteristics (A and E grade briar block only). If you can get a pick of the nomenclature, I may be able to peg down the production date within a couple of years.
You can find a whole lot of information about Grabows (and the other Sparta produced pipes, Linkman, Kaywoodie and Yellow-bole/KBB) through the Dr. Grabow Collectors Forum.
50s-70s non-filter Grabows are ridiculously good smokers; I have two that I bought as NOS. Irishlefty on ebay (no affiliation) occasionally has them. Just don't bite too hard--the bits will break. I use softee bits on mine.
Pipes usually have stamps on the side of the shank that will give you some info. Sometimes it's just the country they were carved in, others may give you some combination of the Brand, Line, Shape, and Date they were carved, sometimes this is coded. Most popular makes have some sort of symbol on the stem, Sometimes it's the same symbol for all pipes from the maker, others have different symbols for each line of pipe.
Pipephil.eu is a good resource for researching the symbols and dates of a pipe.
Rather than make a new thread, I figured I'd post this here. Several months ago, my adjustomatic Dr. Grabow became very corroded in the screw tenon section. After some prying and jostling, I snapped the aluminum tenon. That sucked because it was my first pipe. Now I'm looking to replace the hole in my collection with another cheap briar. Naturally I fell back to Grabow estates. And another adjustomatic. Is there anything I can do to prevent this from happening again? Should I disassemble the pipe after every smoke? Is there some compound I should put on the tenon?
If it happens again I'd try putting it in the freezer for 30 minutes. This works with vulcanized stems and briar shanks. I don't think the aluminum was machined to such a tight variance that a little heat or cold wouldn't fix it.