Check out this link... Coloured Field Service Caps
I thought it was a Fusiliers Mont-Royal - other ranks, but the piping is wrong. If you don't see it in the list you might want to contact Clive...he's a good guy and will probably ID it correctly for you.
Ya isn't that an awesome reference page! I asked Clive a few years ago & he couldn't ID it either. I'm hoping someone in the UK can help as it looks to be made there from it's style of construction.
I think its probably a case of the yellow crown fading in the sun / rain so it appears white. Is it an off white colour like it is in the photo?
No it's not faded as none of the other colours are & I can see the white,yellow & red where they are sewn together on the inside.Yes,the crown is an off-white.Still a mystery.
some of the British corps have white crowns to the coloured fs cap like the pay corps but this cap doesn't match any British caps or Canadian, but you probably aleady know that. I'm not savvy with Aussie or NZ caps also there are South African FS caps and others to research. I have a few caps I've never id'd, Ive assumed they were college or TA caps or obscure Empire regiments.
Heres another example of one of those coloured fs caps I picked up in England on the weekend. The same as the other one except this has a cut for a slider badge. Still no closer to id'ing it though.