Identifying a transistor marked "N 842"
This is probably a transistor labeled with a internal company part number.  This is even more likely since you say you get mostly used parts in your area.  The part is unlikely to be used, but it sounds like your market is the kind of place where overstocks of private-label parts often end up.

Assume you're not going to find a datasheet and go from there.  Don't use this part in production or in a demanding application.  Otherwise, you can measure the basic parameters well enough for most purposes.  You can determine NPN versus PNP directly, get a good idea of gain by measuring, and the package gives you a good idea of power dissipation.  Other than that, just don't assume it's good to particularly high frequencies or high voltages.  Treat it like a small signal transistor good for 30 V and you will likely be fine.

If you want better specs, buy something with better specs.