This is another fascinating derailleur. It is a fairly faithful copy of the famously crude and ugly 1980s Simplex SX1 (or Alpha) - but with its own quixotic flourishes. Dig those glossy pulley cage plates.
It has 'SPARK' carved into its outer parallelogram plate in a touchingly simple but accurate way, and also has 'SPARK' cast onto its p-knuckle. From this I cunningly deduce that it is manufactured by Spark Engineering of Ghaziabad, India.
I bought it from a person in the Czech Republic. How it made its way from the fragrant suburbs of New Delhi to the stag party capital of Central Europe remains a mystery to me.