The Diplomat used a rear catcher, where the more common (chain drive) SBs had a front catcher. I don't know how rare those catchers are - Deejay will know and can probably suggest how you may find one, or one of the members may have one.
If your B&S is 1982 or later it has Magnetron (breakerless) ignition. If it is pre-1982 it has breaker points. You can find the manufacturing date from the series of numbers stamped on the engine's cooling cowl: the first two digits in the third (last) block of numbers are the last two digits of the year of manufacture (e.g. 76061708 means the engine was made in 1976).
Once the engine is running properly, you will need to have a look at the rest of the machine - in particular the clutches and the cutting system: the reel and knife. I noticed that your reel has not been resharpened much, if at all, so it should last a long, long time with proper care. The bedknife may be rusty, though. If it is severe it is likely to cost you money.
