Here is an image of what Silverson thinks is the oldest Silverson mixer still in operation.

The mixer shows the company's previous trading name 'Silverson Machines (Sales) Ltd', this was changed to 'Silverson Machines Ltd' in 1948 so the mixer pre-dates this! The mixer is still being used for R&D at an automotive polishes manufacturer.
Also, Silverson asks for information about the older model of the homogenizer if there is any which can one more evidence of robust and high-quality equipment by Silverson!