The three "Jumbos" I have held have all been pretty much to the pattern of the colored print above.
It is my understanding that about 110 .500 Schulers (the Jumbo) were made in total. I bet that a few others made guns for the .500 as well and it seems that W.J. Jeffery made their iconic .500 Jeffery in response to customers' demands for a bolt gun with the power of the larger nitro double rifles so made their .500s to use the already in production German cartridge - the .500 Schuler - although there are slight differences in the cartridges.

Here is mine (my son's actually).