I have a modern slow cooker which is oval, huge, and would feed half of Bengal per batch. I really needed something smaller as I'm the only curry eater in the family - something around 2 litres.
So I started looking around charity shops and came across an original Monier Crockpot. I don't know about the UK but over here they were introduced in the late 70s - the concept died out in the 90s but has been revived in the last ten years or so. In Oz if you say "crockpot" everyone knows what you mean.
I found the device (in orange of course to match your funky Life on Mars kitchen ;D) in a Lifeline (= U.K. Samaritans) shop. Only cost me 6 quid UK money. All electrical items in charity shops must be tested by a sparky, who do it as a community service. Unit works perfectly, I'd guess it's around mid 80s.
So, Sri Lankan Chicken on the bone curry cooking up at the moment, I'll post a pic on serving.
The thing that impresses me about Sri Lankan cooking is that, being a smaller country there seems to be a bit more consensus on recipes than the vast Subcontinent - if you look on various sites the ingredients and methods are fairly consistent. Especially the use of coconut milk, coconut cream, creamed coconut, toasted coconut.. did I mention coconut at all?

Also curry leaves by the wheelbarrow load. Fortunately I have a couple of trees on the go.
With the money I saved I
finally bought an electric spice grinder, and made a big batch of Sri Lankan Roasted Curry powder.