Well...I think that the conclusion it is that there is not a final conclusion! Probably there are so much "not very official" practices and variants to be sure...so I think that a Rifle Brigade is the more apropiate...but KRC too...so while I think about it is possible that complete the cap wit the D Cornwall I have...and in the future and with more information I will change it...(or not!
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Thanks a lot to all of you for your kindness and usefull help!