This large, charmingly worn enamel sign for Holdfast Boots is the biggest example I've encountered. The centre of the sign is embellished with the company's iconic reef knot logo and this is set against a background that has faded to a pleasant teal green. The sign itself probably dates to around the 1920s.
Obviously enough the background colour is as close as this sign comes to 'mint' - there's heavy enamel loss along the right side edge as well as discolouration, surfaces scratches and rust stains, but in my opinion, these all form part of the sign's charm. They also mean that despite the strong following for Holdfast advertising you can own this piece for significantly less than many smaller examples.
The sign measures 1.4m high by 99cm wide and despite the patches of corrosion can still be secured using it's original mounting holes.
There is some warping to the sign (most notably the lower right corner) but it sits reasonably straight once hung.