Skilled radio assistance please!

[Mike Watterson]

Was there ever a "standard DIN" all valve car radio?  I am sure I had one many years ago.  I know there were transistor output ones using 12V valves, what about vibrator (proper HT) and valve output?

Actually they were regular valve run at 12 to 14HT. The "12V" ECH83 is just a rebadged ECH81 (not even specially selected) and run at about +1V bias.
https://www.radiomuseum.org/forum/ech83_qru.html#3

A number of other valve work at 12V HT with suitable bias. I think EF89, ECC82 etc.

DIN mount car radios were probably after the valve era.

Founded in 1917 as the Normenausschuß der deutschen Industrie (NADI, "Standardisation Committee of German Industry"), the NADI was renamed Deutscher Normenausschuß (DNA, "German Standardisation Committee") in 1926 to reflect that the organization now dealt with standardization issues in many fields; viz., not just for industrial products. In 1975 it was renamed again to Deutsches Institut für Normung, or 'DIN' and is recognised by the German government as the official national-standards body, representing German interests at the international and European levels.

—Wikipedia.

There were / are many DIN standards (DNA from 1926 to 1975). The 3 and 5 pin connectors on 1950s German radios etc later became DIN connectors. Later there was the mini-DIN.

So valve car radios might have referenced various DNA standards, I never heard of an overall one, or later DIN for transistor car radios. The mounting was only one DIN standard. Measurement of distortion, power etc would be a different DIN, connectors a third set of DIN standards.