Royal Enfield's old Albion gearbox tells a story

Royal Enfield four-speed gearboxes, separated by 40-plus years.
My 1999 made-in-India left-shift gearbox is at right.

I've only just praised the obsolete Royal Enfield four-speed gearbox on my 1999 Royal Enfield Bullet, and along comes an eBay advertisement for a similar but obviously far older example of the same thing.

And, my, doesn't it look familiar?

There are differences. The older one is right-hand shift, of course, as most were. Only where legally required were they made to shift left, as is mine.

Note oil filler plug at top right of gearbox. Mine has one there, but...

But, wow, get a load of the bolt that covers the top oil filler hole. Stamped on it — in oh, so tiny type — are the oil specifications for the gearbox.

Castrol, Mobiloil, Shell, Essolube, Energol. Great old names that mark this gearbox as a product of Redditch, England.

...the older gearbox filler plug is labelled.

The poor filler plug is a bit bunged up but I would love to have it. The filler plug on my made-in-India gearbox is plain.

I'm a little surprised that the filler plug specifies oil.

My understanding was that gearboxes back then were filled with grease from the factory, as there was no proper seal on the sprocket side to retain oil.

My 1999 gearbox came from India filled with what some used to refer to as "elephant snot." That stuff stayed put.

When I tried using oil the gearbox it soon bathed everything behind it in oil. At a sprocket change my mechanic fit a seal, and oil has worked fine for me ever since.

Canadian Royal Enfield enthusiast Chris Overton kindly identified the old gearbox, based in its serial number, as being from a 1965 Series 1 Interceptor.

I wonder what stories this eBay gearbox could tell of its travels.