I happened across several cartridges from Japan with a black switch protruding from the front of the case. Each has a crude, circular label with a single digit number on them, black case and contain a game. Were these used for development or competition? The little I can find online so far indicates they could be prototype cartridges. Thanks in advance
Sounds more like those programmable NROM cartridges used by a pirate device. The switch is probably for setting the mirroring (AKA scroll) setting, which depends on what game is programmed to it.
That's correct - don't rush to believe any speculation that carts with switches on are debug / dev / test / or sample carts - generally they are just pirate / bootleg releases.
Still fun to come across and collect for - but not the rare development items they can sometimes be pitched as, in an effort to command a higher price. A picture would help to clarify.
Nintendo did use dipswitches in later systems like GB, GBA, DS, but I have never seen an official Famicom version of this - because manufacturers generally made their own boards and shells.
Thanks for the info, attached is an image for clarification.
Here is the device that uses them: https://famicomworld.com/system/other/fami-corder/
It can only write NROM games (Donkey Kong, Popeye, Tennis, Mario Bros, Super Mario Bros etc) I think.
Is there a video on this so we can see the cart in action?