/\ That's close enough for me, its actually a Slavia D8 engine, they were available as a single cylinder engines in 5, 8, 12, and 16 HP versions.
Here is a photo of its bigger brother in the background of this photo, this was a 12 HP version (see how tiny it makes the Listeriod crankcase look by comparison), the 16 HP version is considerably bigger again.
Now returning to the Lister theme, what about this:
And what about that crankcase 1/2 way up the LHS of the picture?