Nice find Dave. The one on the left is the second version (of three) of the original sand cast 19's dating from February 1950. The head and prop driver were originally anodised red and there's a trace of the anodising left in the knurling of the prop driver. The main identifying feature for the second version is the straight sided head fins. Very little is known about these early sand cast .19's so it's a bit of a rarity.

The one on the right is the first die cast 29 made after the original sand cast Typhoon and dates from early '54 and there were two variations but I can't pick which one yours is from the photo. It's not known for a certainty which came first but there's a difference in length between the exhaust ports, one has a port that's 36mm long and the other is 38.5mm long. It's been decided (because Enya themselves aren't certain ) that the longer exhaust is the later version for various reasons.