Some red flags here. Early on, there was some Monnin quartz made with 844 reference. When Heuer took production in 1980, the reference for a automatic with ETA was 844-1. The quartz as referenced above was reference 980.006. Do you have a movement pic and any pics of the case back (inside and back).
Personally, I don’t believe in NOS watches. There is only condition. Excellent, Very Good, Good, Fair, Poor or scales 9 out of 10, etc.
Hands have most defiantly been replaced. Will be nice with correct mercedes style. Let’s get a feel for movement, and see if case back is correct.
Here is my Late 1979 Heuer 844 “Monnin transitional” with non 24hr dial- cal. FE4611-A. Condition - Excellent. These were the last of the Monnin’s and likely were a cut-over between Monnin and Heuer. These still have 844 model on back, FE4611-A, Made in France and “professionel” dial. Have seen Rotor etched G.Monnin and Heuer. If memory serves me, some case backs have Heuer-Leonidas etch.