What is exactly a 616/6 engine ?

[Thierry Bingen]

My 1961 356 B T5 Coupe is (unfortunately) no longer equipped with its original 616/1 engine. Its current engine is a 616/6 (S/N P*03747*). I have tried to research this unusual model and was only able to find it listed once as a "1600 universal engine" (not "industrial"), made between 1957 and 1962.
I wrote to Porsche (Germany) which redirected to me to Porsche France, where the car is now registered (after having travelled through Switzerland, Germany and Belgium):

Sehr geehrte Damen und Herren,
vielen Dank für Ihre Nachricht an Porsche. Um Ihr Anliegen beantworten zu können, brauchen wir ein wenig Zeit. Sobald alle Informationen vorliegen, werden Sie von einem unmittelbaren Ansprechpartner oder uns wieder kontaktiert. Bis dahin bitten wir um etwas Geduld.
Mit freundlichen Grüßen
Porsche Customer Relations

This totally unhelpful answer was followed by an even worse, dismissive message from Porsche France:

Monsieur,
Nous faisons suite à votre message concernant les caractéristiques du moteur de votre Porsche 356 B qui a retenu toute notre attention.
Aussi, nous nous sommes rapprochés du service concerné qui nous indique que ces informations sont internes. Aussi nous espérons que vous comprendrez que nous ne pourrons donner une suite favorable à demande de renseignements.
Comptant sur votre compréhension, nous vous prions d’agréer, Monsieur, l’expression de nos salutations distinguées.
Sébastien Berger
Relations Clients
Porsche France SAS
25/29, quai Aulagnier
92600 Asnières-sur-Seine

So my question is simple: does anyone out here know what this mysterious "616/6 universal engine" is ? From the outside, it looks like a 616/1, but it ain't.

Thanks for your help !

[Jules Dielen]

It is an early industrial engine.

http://www.356a.com/engine_identification.php

[Thierry Bingen]

Thank you Julien.
I still wonder why, in the list that I found, only the 616/6 and 616/20 (1500) are designated as universal and not industrial like the 616/3, 3R, 5, 8, 13, 13R, 18, 21, 23, 33 and 33-1 (or "special" like the 616/11).
The referenced site is also imprecise as to the destination of the various industrial (and universal) engines.
The mystery remains.

[Martin Benade]

I wonder if the /6 is equally detuned.

[Jules Dielen]

Depends on whether the magneto is 50hz or 60hz. Iirc at 50hz is was rated for 3k rpm and at 60hz it went up to 3600rpm?