Yeah no such thing as an HSTAT control on a Hanty, you don't find controls like that on arcade monitors usually (not that i've seen anyhow). Your crt sounds like it's a Videocolor (I think Thomson made them), which were statically converged at the factory using a machine, sometimes using a permanent magnet round the neck (apart from early ones for the 900 and 900/E which did have rings built into the yoke assembly), the permanent magnet is usually seen on 25" and larger crts. Other crts like Orion used a normal ring setup. If the convergence is uniformly "off" across the screen you can as said above use a normal set of rings on them but it can be tricky to set them up sometimes. If it's just out in the corners, you may find you can improve the edge or corner convergence by using small adhesive magnets on the rear of the crt. Some of the larger crts did this from the factory using V-shaped adhesive magnets.