Funnily enough Mark I have just come across a 410 Special in the free ads.
It looks to me like Mitchell were testing the market when they launched the 440 Special. I have seen them for sale in Germany and France, and the serial number of two of them refer to 1964, 2 years before the 410 and 440 were launched. Nobby seems to think that the UK concessionaire distributed some reels to match anglers to get their views on the pre production samples. The 440 had the non roller bail. By the time it morphed into the 440 Match it gained a roller bail. Otherwise it was identical to the 440 Special until around 1977 when the 'A' suffix reels were launched.
I haven't had chance to try it out yet, but it has been paired with a Chapmans 500 Avon type rod as they are from the same period.