Recent Sales--500U, 500H, 500P "Mushroom" Phones

[david@london]

are there any mechanical differences between the 7a dial and the 7c/d ?

or was the c/d designation adopted purely as a way of denoting the fingerwheel type ? 
thanks.

[unbeldi]

are there any mechanical differences between the 7a dial and the 7c/d ?

or was the c/d designation adopted purely as a way of denoting the fingerwheel type ? 
thanks.

The 7A had undergone several small changes already, including the change in molding of the number face plate. For the 7C, the governor was changed using a spiral spring, rather than a coiled stretched spring for weights, which continued for the 7D. I have to look up the rest of changes, though...

7C was used starting in 1953 with the color sets, on the black sets the 7A was upgraded to 7D in the second half of 1953.
The illuminated dials were available in April 1954, acc. the AT&T Events book.

I found a discussion thread on this topic here: http://www.classicrotaryphones.com/forum/index.php?topic=2660.0

[poplar1]

500U Conversion; original date was 12-56
Sold for $725.01 Sept. 7, 2014
http://www.ebay.com/itm/111452399519

[Kenton K]

are there any mechanical differences between the 7a dial and the 7c/d ?

or was the c/d designation adopted purely as a way of denoting the fingerwheel type ? 
thanks.

The 7A had undergone several small changes already, including the change in molding of the number face plate. For the 7C, the governor was changed using a spiral spring, rather than a coiled stretched spring for weights, which continued for the 7D. I have to look up the rest of changes, though...

7C was used starting in 1953 with the color sets, on the black sets the 7A was upgraded to 7D in the second half of 1953.
The illuminated dials were available in April 1954, acc. the AT&T Events book.

I found a discussion thread on this topic here: http://www.classicrotaryphones.com/forum/index.php?topic=2660.0

The way the main spring mounting is also different. On a 7C, the spring holder is 'locked' on to the shaft. On a 7A, it is seperate from the shaft.

And on my (one) 7A, the governor spring is a 1 loop wire.

-Ken