I had a look and there is nothing in the Vorschriftenhandbuch about a summer or lightweight version without lining. I don't see anything in the RJF Verordnungsblätter / Mitteilungsblätter about such an item either.
The leader Dienstrock is described in the 1936 RZM manufacturing regulations as having a lining and later in the RJF Vorschriftenhandbuch (large 1938 order concerning new dress regulations) the lining is also mentioned (see pic below). Having said that, this item was made to measure by authorised tailors so an argument could be made I suppose that some had a version tailored for summer without the lining. I don't know but it wouldn't have worn well as it would have snagged on the shirt and then there is the matter of applying an RZM label to an item that actually didn't satisfy the regulation in full. That doesn't mean that a Dienstrock without a lining isn't from the period but Angolia seems to suggest that it was an official item but that isn't actually borne out by the regulations I'm looking at here.
Certainly as far as the regulations are concerned I don't see any mention of a summer-weight Dienstrock so we can only speculate as to why Angolia is so sure that it was an official item.
The dress regulations in the RJF Vorschriftenhandbuch list exactly which items belonged to which form of dress in summer and winter and there is no distinction made between the Dienstrock in either season.
In 1938, a special DJ leader Dienstrock in the same cut and style as the HJ version but in marine blue was introduced. However, that order was rescinded in Feb 1939 by a new order stating that DJ leaders were to wear the HJ version but with a special rune patch (see pic below).
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