Is it a No 6 or a Mark Six? For some reason Youngs decided to cause immense confusion by producing two reels of slightly different design with essentially the same name.
The No6 is blue with a silver flyer and is in shape not dissimilar to the earlier brown versions. The Mark Six is almost all blue except the back plate, handle and spool which are black; it has the same body shape as the Delmatic, which was a slightly cheaper version of the same reel made by Youngs but badged by Allcock.
I've got several Ambidexes including a Mark Six, all of which are perfectly useable, although somewhat heavier than my beloved Mitchells. The Mark Six is probably the best of the bunch as it has something resembling a line roller (although is doesn't actually roll) in the bale-arm; the earlier versions having just a hardened steel wire arm which was prone to grooving.
Both the No6 and the Mark Six date from the 1960's. If I had to put a date on them I'd say around 1962 for the former and 1966 for the latter.
As long as you don't try to cast a hundred yards with it, or expect such an unfamiliar reel to perform perfectly to land a monster carp, you can have some fun using it. Load it with five pound Maxima and have a go for some tench or chub.
You may even get the bug for collecting and using older tackle which, if it does nothing else, will force you to learn more about watercraft and keeping things simple; in the long run this can only help improve your fishing.