Many thanks to John Milewski for these excellent pics of his rare Diana 42E ("E" because it had an English-style pistol grip stock).
The rifle is in .22 cal and is the example featured in the April 2012 issue of Airgun World. It is about 43 inches long, roughly the equivalent to the BSA no.4 Club Standard, which was available only in .177 cal. The Diana 48 was around 45 inches long.
The date 10.31 can also be seen under the cylinder when the trigger guard is removed. "DIANA-LUFT-GEWEHR" is stamped on the top of the barrel and "Made in Germany" under the barrel. The stock is just over 13.5 inches long.
It's interesting to note that this rifle has the earlier goddess Diana marking (ie. the one showing more leg!) on the cylinder, which would seem to date the use of this symbol until at least October '31.
The Vintage Diana Forum
The Vintage BSA Forum