Other Young frames through the 30s? - Easicast, Aerial, most everything else (except for occasional Osprey) in the Allcocks or Milwards catalog.
I've had these earlier examples (and several others), and have sold them (look up a few posts and you'll see why)
here's an early 20's (or earlier?) Allcock Ousel finished by Young
Is this the pattern 1-A frame? I need to ask Rupe...
I believe this same casting was finished out both by Heaton and Young and likely before the end of WWI. The Heaton reels show the drilled-hole medium arbor, the foot is riveted the way Heaton would do it, and it has the scribed marks inside. The Young foot (above) is two screws with one additional brass pin.
Andrew R., owner of Heaton, came through with a catalog listing that shows this style reel was made by Smith & Wall, so this pattern with the large spindle nut on the backplate is not a Heaton reel, and I have the incorrect catalog listing below.
added this 30ish catalog recently and I believe this is the same reel
earlier Heaton alloy reels used this casting, coined edge (look familiar? this is the 2-1/2" version of your A&N reel). Note that the posts are soldered, this is not a one-piece frame casting.

1919 Heaton catalog

this same reel was sold by William Mills in their 1912 catalog. Unfortunately, they didn't update the drawing through their 1940 catalog, long after the reel being sold by Mills (with this picture) had been replaced with a Young pattern 1c standard grade...
so the solid frame casting is definately by 1920 and likely 1915? (Rupe Atwood recently listed a very early pattern 1c click-pawl reel as early 20s, and he knows better than I) I'll keep looking to try to verify this date.
p.s. found the 1-pc. cast frame in a 1917 Albert Smiths of Redditch catalog, which confirms early dates
The oldest alloy frame I've seen that I think may be Young is this one, and is likely earlier than 1910. The alloy is horribly soft - to the point that you can tap these parts to any shape you want:

Brindley John has had the same reel (just above) listed on his site for several years as a Dingley, but I believe it is definately older, and certainly not up to the quality of the first Dingley Bampton reels, c. 1912 (the difference is night and day):
Of course while Young/Allcocks and Heaton were the biggest shows in town before WWI, they weren't the only ones. Before being bought by Allcock or Milward around 1920, there were Dreadnaught, Slater, Percy Wadham, and Moscrop making reels independently. There was also Smith & Wall, which has been mentioned to me as possible maker on the square-edged solid-frame reels I attributed to Young and Heaton.
The Duplex was patented in 1893, and the Simplex in 1895.
http://www.antiquetackleobserver.com/in ... 6&Itemid=9
look in the fine print for Youngs of Redditch and click
These reels were brass frames, with ebonite and alloy used on the spools.