Caps made by Wilhelm Welhausen are desirable because of their relative rarity, their quality of manufacture (which is very high), their very high crown with its fantastically characteristic saddle shape, their frequent use of leather visors and they are famous for sporting thick "chin cords" - also they were very expensive and desirable caps in their day which this price list illustrates (thank you Chris/stonemint):
In fact I will be posting a prewar made Welhausen with a soft leather visor in a little while...
I agree, WW caps are the most underrated maker of the TR. Most have never even heard of them. What makes the company different is that they were not just a hat-maker, but a tailoring house as well, which shows in their finished product.
NEC SOLI CEDIT
thank you all who have helped me with the information very helpful