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AFTERNow this is a pitty, the missing before shot of this engine was a sad case indeed. The "After" shot here is my actual first ever anodizing job, and through blind luck and ignorance, it came out just about perfect with a deep lusterous, shiny finish. The engine is the one that followed the Bubble Pack Taipan 1.5. The NVA is correct and I recall buying one of these from the Hamilton Cycle Store to replace the one in my bubble pack engine that would just not stay still (and was considered to be some kind of nut by my primary school flying friends--who ever heard of replacing a part that was not really broken?!)
This side by side shot of my first two Taipans restorations clearly shows the stronger, longer lugs on later model. The one with the round shaped head is an example of the "Bubble Pack" model made in 1958. A 100% genuine "Bubble Pack" Taipan would have a split thimble needle valve. The one here has the later stepped spring version; a result of crash damage replacement (more than once!). The other is a 1960 series. The obvious difference is the head shape and the stronger lugs that extend onto the front journal extension (the mounting hole pattern is different, too). The (very rare) 1959 model can be differentiated from the 1960 series by the shape of the crankcase journal extension. On the one here, the casting tapers to give greater strength where it joins the main case body. The 1959 model was parallel, as was the 1958. If you look closely you can see this in the photos.
From 1960, all models had needles which were stepped and fitted with a spring, as seen "After" photo. There is also a subtle difference in the drive washers. The older model is made with a radius between the horizontal and vertical parts, while the later one has a sharp transition. You notice these things when doing restorations...