I don’t think you are. I believe the convertible was only produced 1962-3, the 1725 only appeared in 1965 in the mk 4. I think it would be a 1600, I’ll have to hit Wikipedia to check. Don’t have time to look now, it’ll suck me into a rabbit hole as usual and I’ve things to do!
I have the benefit of knowing the registration number (unless my brain scrambled it in the five minutes it took to walk home, which isn’t wholly impossible). 1725 is what it comes back with on gov.uk’s lookup.
1725 is what it comes back with on gov.uk’s lookup
It’s certainly possible, I think the 1725 was essentially just a bored out 1600 so probably a simple drop in swap. 1600 will be what it left the factory with but there’s a lot can change in 61 years!
“root(e)s group”
Rootes it is, Sunbeam was the sporty marque, Humber the posh one and Hillman was the boggo cooking variant.
My money’s on it being a Hillman Super Minx then, I thought you’d said it was a Super Minx a while back? The other Rootes equivalents to the Super Minx are the Sunbeam Rapier and the Humber Sceptre and I’ve never seen either of them as convertibles in the wild, I’m not even sure they made them, as convertible was already a bit of a niche market.