Here are a couple of photos of an old suit. Inside zips, and the separate zip fly going under the crotch as you mention. Colour was a more green colour though. I guess there are of course differing shades of grey and they can be seen here by the patch on the front groin area which looks more grey than the surrounding green. The Beadon suit on ebay a couple of weeks ago was a very 'battleship' grey, and the label had a very late stores ref number, post 22C type.