Hi Dom,
Sorry for not answering your previous post, it was on my "must answer that" list and I forgot about it.
Most of the Rohr Stuff is in French and German, I assume there is not enough interest in the English speaking world to justify translating it.
A guy called Patrick Schallert has a website with many, many Regt and unit histories availible on DVD, about EUR5 a pop. It is useful when you need many, many histories for your archives. I usually only buy the original book when it is a unit I am very interested in.
The last Rohr History I saw on Ebay went for quite a few hundred EURs,
Why dont more have the crown and "W" badge... a good question. I am not sure how widely spread the wearing of the badge is. And the kaiser apparently did not approve it.... See these Guys from Rohr at the kaiser HQ in November 1918... none of them have it...
http://gmic.co.uk/index.php/topic/60752-most-exciting-photo-of-my-year/
Best
Chris