Reviewing the FH albums, there are definitely GR pics in there ('Mite Wagon' thru to 'Auld Tubs') Frazers dib had a big square steel gate with possibly a diagonal brace; GR Firestone decline now has a similar one but made of heavier steel and with a vertical brace.
The arched gate in your pic of FS seems to be an early fitment, probably centre-opening-hinged-both-sides, and being replaced by the heavy hydraulic gate later.
Hope this is helpful
MARK