So you just rediscovered the Commodore 64 and want to take a stab at writing some applications in 6510/6502 Assembly?  Then this might be what 
you are looking for.  This software will allow you to program in the native 6500 series Assembly language code, directly on your Commodore 64
computer.  It contains a macro Assembler, editor, loaders and two machine language monitors along with other support routines.

You will receive: (1) One 5 1/4" Floppy Disk containing The Commodore 64 Macro Assembler Development System

For additional resources, the Manual can be found online as well as youtube videos on how to use this development system.

To use you can (among other programs):
- Type: LOAD "BOOT ALL",8 and then type RUN

The is not a cheap, no-name brand but a new, original, tested and working 3M diskette.  I'm reducing my collection of diskettes and will have more and different titles available. 

*Comes from a Smoke-Free and Pet-Free Home