What is the difference between these "dials". 7C and the 7DX?

[Contempra]

Good evening, I bought this afternoon a telephone model 500 with a Dial 7DX dated January 1967. I usually find Dials 7C or D, but the one I cleaned and lubricated this afternoon. For you, it may be common and you know the differences

My question is ; What is the difference between these "dials". 7C and the 7DX? I ask since I don't see any differences between the one I did (7DX) this afternoon and the 7D?

Sorry, I don't know how to ask the question properly.

[poplar1]

7C is a dial for color phones. 7A and 7D are black.

I don't know about 7DX. Can you provide a picture of the back?

[Contempra]

I will try tomorrow during the day. I just put it back together, so it will be fine tomorrow. Thanks for your reply Poplar. (I don't know your first name.)

EDIT : The phone is approximately 'salmon-pink' Dated  january 1967 and it's a Nothern Telecom .

[HarrySmith]

Interesting, I also never heard of or have seen a 7DX. We need pictures!