By general operational employment I am referring to general Squadron use, i.e. How many aircraft were equipped with it and at what date. Most publications on the 109 refer to Auto as a late 1940 introduction.
the JG53 account above is a typical example... "17 Sept 1940". As are the references to it in the book Messerschmit BF109 Recognition Manual by Marco Fernandez-Sommerau page 103:
"A significant improvement from mid 1940 was the adoption of an electro-mechanic automatic pitch regulator ..."
The AJ Press publication on the "ME 109" Pt 1 page 46 refers to it being tested in "Summer 1940".
The RAF and French test reports on the E3. The RAF handling notes on the E3 all refer to the non auto version.... though I presume these are all based on the same aircraft.
The Translated document referring to its initial introduction of auto.... "has been introduced" , though I accept the hand written date on the document isn't iron clad.
Steinhilper's book "Spitfire on my tail" refers to manual prop pitch use in Sept 1940 and the difficulty on training new pilots on the technique to use it to maximise performance.
So I am not so sure its "Its rather safe to assume that all new production aircraft had it (for example Emils produced in 1940), while the older machines were gradually retrofitted with the system." Late 1940 production I would agree with as I would for earlier aircraft being retro fitted.
The general thrust from various sources is that general operational (i.e. squadron) use of auto didn't occur until late 1940. Thats not to say that Auto didn't exist conceptually or limited use prior to then. Based on the general knowledge it would seem that Manual was the most common system until at least Sept 1940 i.e. the Main accepted time line of the Battle of Britain.
In the end we are then discussing how all this info translates to COD use. So far the E3 and E3B are the Manual system. I would anticipate the E4 and later models when they come to be equipped with the Auto system. A datal based system could also be applied to E3's allowing Auto use post Sept/Oct 1940 ? . An intermediate step might also include the Rocker switch on the throttle with Manual as well.
Kurfurst what is the exact date of the Handbook and or its last amendment date from which you refer ?