Original style distributor cap, flat top style for very early 25hp engines, where the leads enter the side of the cap. 

For the ignition leads for this cap, please see-

https://alanhschofield.com/ourparts/prod_8212637-Ignition-Plug-Leads-ALL-Aircooled-1200cc-1600cc-BBT-Production-111998031A.html

These leads were specially made by BBT Belgium with the 25HP application in mind, so just need the ends discarding before use.