JDW, that's if you have a boot floppy present. Just looking at the machine, assuming it doesn't power up, or don't have access to power. If it does power up and you don't have a 400K formatted floppy disk (to boot under both 400K & 800K drives), like many eBay sellers or garage sales, there is an even easier test. Press the interrupt button (or use a paperclip if it does not have one) and 64K ROMs will give you a Sad Mac. 128K ROMs will give you a C prompt in a debug console.

Scott, you don't even need to stick a disk into the floppy drive to see the difference between a 400K & 800K drive. The 400K drive will be eerily aglow with red LEDs. This is of course assuming it powers up to being with.

Ultimately the check list should be as simple as possible:

1) check the serial number – it will end with one of the model numbers listed on the agency label below: this is ultimately how the compact began life regardless of anything else you may find.

2) check the agency label – M0001(P), M0001(P), M0001W(P), M0001E, M0001D, M0001ED, M0001A(P) – This should match the serial number, otherwise the rear bucket has been replaced.

3) check the rear label – Macintosh, Macintosh 128K, Macintosh 512K, Macintosh Plus – This should correspond to the model number, or else it has been upgraded, and/or the rear bucket replaced.

If the compact powers up

4) Check for RED LEDs in the drive slot, this will confirm an 800K upgrade if a 128K or 512K, or a downgrade in the case of a 512Ke or Plus

5) Press the interrupt key, this will confirm the presence of 64K ROMs or 128K ROMs.

6) With a 400K startup disk, open About Finder and the resulting dialogue box will confirm the amount of RAM available.

That's pretty much it. Now you know everything about your Mac you can without opening it up, or possessing special software.