Can't help with the date of the badge, though I also have one, but your car brought back memories as my dad had one the same colour and year. My first car was a 1956 A35, the forerunner of yours. I owned it for almost 30 years. The best 25 quid I ever spent - 210,000 miles and itwas still on the original engine

Who says cars now last longer - a bit of TLC was all that was required
I moved on to a Rover P4 (which I've now had for 20 years) - it doesn't come out of the garage at this time of year
Steve