I think it dates back further than Marks' entry. The origins of the developer is one of inconsistency and rapid failure when using the 1 Ltr package. A robust and straightforward developer it is but there is the lingering fear that my next batch might fail or go up in flames . Marks entry is most welcome and when finally refined will be a delight and comfortable alternative to Kodak's if only for the smaller amount of concentrate needed in-house.