Rolex Root Beer dial

[Slawek]

Hello,
Do you know when Rolex introduced non-nipple dials for Root Beer reference 16753?
I found somewhere information that these new dials were introduced in mid-80-ies. I'm considering a purchase of a Watch with late 6 million case number which dates it to 1980-81. Isn't it too early for a non-nipple dial? The dial is Swiss T<25 type. Could that be a service dial which replaced the original nipple dial?
I attach the picture.
Thank you in advance for any suggestions.