Well, after asking around and looking around on the internet and in various books I have, I have come to the conclusion that that best symbol of Dieselpunk (or diesel punk) is wings. The era of diesel punk saw heavier than air flight take off (no pun intended :)) in a way that no-one would have envisioned. People were suddenly able to travel much faster than previously. Although it couldn’t be said to be safer once sky pirates realised the potential.
To conclude. The symbol for AR Dieselpunk books will be the AR symbol with wings to the left and right. Just need to get the graphic designer to get designing!