Battery Radio with "fine adjust" on the rheostats?

Thanks for the info. Maybe Globe Electric added them for a "bragging point" in their advertising.

No, I have not seen filament verniers on "factory" sets.

IMHO that would create a set specific for DX work, something that would be a niche market for manufactures. At most would be a separate rheostat for the filament.  FWIR, some manufactures used the Bradleyohm filament rheostat. That is a carbon pile compression device so infinite variability is possible. I think that reviewing the archive, American Radio History for Bradleyohm may reveal ads that report the use of the product by an OEM... I know that Thordarson did this with their transformers...

Any receiver with DX in their model name for example Federal DX, I have not looked at that receiver but it is likely to have such a vernier rheostat...

Discussion of detectors in general took place in the early 20's magazines, the ARH search may work but only downloading and scanning the articles may work. If there is a an article there may be a radio advertised to take advantage of the readers curiosity...

I have a Cutler-Hammer vernier rheostat, I also think there was a Yaxley.

If your really want some images I can pull the box of filament rheostats and take pictures  for your archive...

The real fun would be building a set that uses one and actually see it perform. I would think it would be with a gas detector...

YMMV

Chas

Have you ever seen them on a manufactured (brand name) radio?

FWIR there is a couple of homebrew battery sets in my collection with the fine adjustment of the filament rheostat on the detector. I have a couple of these rheostats in the parts stash. In fact, picked up two more of these vernier rheostats this past fall. Very novel methods to get such fine resolution. Imagine a DX radio fan of 100 years ago tweaking the detector ever so carefully to get the Opera from NYC or the stock market reports in the mid-west, corn futures. Essential entertainment and important financial news. Such fine controls are useless in a radio that does not have the refinements to make these adjustments practical. Like infinitely adjustable panel mounted grid leaks and power supplies with adjustable detector voltages.

YMMV

Chas

I recently picked up a Globe Electric Co. model 815 battery radio. Its the first radio I've seen with what looks like fine adjustment controls on the rheostats. Is that what they are? I haven't found a schematic for the radio yet.