There are seven bids already. Its casing is marked '152' which indicates it was fitted to a Wolseley 9. The proportions of the casing show (apart from '152') that it was a synchromesh gearbox.
Among the pieces on the bench is a synchromesh cone - hardly in keeping with a J-type gearbox.
I shared this information with the seller and he has added the following -
"I have been advised that this gearbox will also fit a Wolseley."
I am sure the seller is honest but I do not think he understands that this is clearly not an MG gearbox let alone an MG J1/2 Gearbox .