The SdKfz 10/4 has armor again

[J6A]

Wikipedia says "Sd.Kfz. 7 armed with a 3.7 cm FlaK 36 anti-aircraft gun (in 1944 switched to 3.7 cm FlaK 43). Again, both open and armored cab variants existed. About 1000 produced by the end of January 1945."

So, maybe the 0 armor is the armored cab version?

It also says "37 mm FlaK36 auf Fahrgestell Zugkraftwagen 5t (Sd.Kfz. 6/2): Sd.Kfz. 6 fitted with a 3.7 cm FlaK 36 gun, sides would fold down to allow space to work on. Crew of seven."

So, I'll guess different ratings are the Flak 43 vs. Flak 36.  Although it seems odd that the version with the Flak 43 has lower ratings.  And the article (admittedly brief) doesn't mention an armored cab on the 6/2.