Dan,
Now that other things in my life have quieted down a bit, I've had a chance to check some old notes on the early days of the 500. I've added some of the material to the site.
http://www.paul-f.com/weproto.html#500Note the shape of the line switch and ringer in the patent drawings. They sure look familiar!
The patent numbers to search for are:
G Handset: 151,614
Base: 153,928
Line Switch: 2,566,840
Ringer: 2,590,500
Has anyone tracked down patent info for the handset elements?
We still need to find a known 1949 set to compare with yours and a 1950 set to fill in the gaps.
In lieu of finding a whole 1949 set, I'm collecting photos of dated 1949 components that have turned up in later sets, such as the 10/49 dial we discussed off-line.
I'd caution reading too much into pre-1950 photos used during the product launch. The Bell System often used design concept sets (often painted plaster models) or field trial sets as subjects for the initial articles (including BSTJ and employee publications) and ads. BSP fans have often commented that drawings in the Issue 1 BSPs often don't look a whole lot like the production product.
Don Genaro (former head of Henry Dreyfuss Associates [HDA]) once told me that numerous concept models were made for housings for the phones from the 500 thru Trimline sets. The wood models for the G handset posted earlier are a good example. You've probably also seen some of the photos that survived for the Princess and Trimline models on my site. We're still looking for similar photos of 500 design models. Most 500 models were apparently small variations on a theme, as the basic original design survived with only a few tweaks due to final component dimensions.
Don also said that HDA had warehouses full of the models for many years, but destroyed them in the 1980s to make room for other customers' models. They also did vacuum cleaners, farm machinery and locomotives, among other products.
The set shown in at least one of the articles I've seen looks like a painted plaster model.
It's safe to say that HDA would have built both clear and black plungers and tried them out in various sets to see how they looked and to gauge viewer reaction. The only thing we know for sure is that black was selected for the production sets.
Typically sets through field trial were made in a batch shop, not on the production line. Once the concept was proved, manufacturing engineers got involved to wring out the last tenth of a cent on each unit. The process continued through the life of the product. I believe that process is evident in comparing your set's line switch, ringer and dial with the production parts.
There are many stories regarding when the aiming dots were added. The Dreyfuss references suggest it was relatively early in the process, and that photos of sets without the dots are probably nonworking design concept models.
More to follow...
Paul