I recently thought about building another purpose-specific 6502 SBC.

I'd like to have a sizeable keypad and a simple alphanumeric display. Those parts I'd have to buy. At least the keypad, I may have a display I could use.

I thought about these: http://www.ebay.com/itm/231598548744

In the distant past, I've thrown quite a number of them in the trash due to physical damage, or just the owner wanting to do something different. I never tried to keep one, as I always assumed other people would be throwing them out too, and if on the odd chance I'd ever need one they should be easy to get second hand. But apparently they are selling for more than I expected. That one is $50 but I see some selling for $300 and up.

These things have a Rockwell 6502, a fair amount of RAM, and a good amount of I/O. I wish I had tried to keep some.

I like this idea!

(Just in case of link rot, here's an archived version:

"INTERMATIC NEXT GENERATION PROGRAMMABLE TIMER ET142402D"
Looks like it has 23-key keypad, 6 digits of seven segment display and 14 indicator LEDs
)

I don't remember what kind of ROM is in there, but it may be pretty sizable. The operation is pretty sophisticated, and they have extensive astronomical and chronological data. Basically they have the capability to turn lights and sprinklers on and off based on sunrise, sunset, and holidays, if memory serves. But that may be on an auxiliary device off the main bus. Either way, I expect that the address decoding as it is, provides for more ROM than RAM.

If there are several models which use a 6502, and some which don't, it would be handy to have a list of the ones which would make a good 6502 project computer.

And indeed, photos of the insides! And schematics if such a thing were available... ... but then it's an interesting project in itself to map out the hardware.

Does such a controller have heavy duty output switches too, or would they be part of some additional unit?

They have a number of high current relays inside. Depending on the model, they have one, two, or four.

In my experience, if it looks like that one in the picture, metal box, 6 digit LED plus the row of LEDs and the big keypad, then it has a 6502 inside. It seems like they used that design for decades before going the China route. I don't know what's in the Chinese ones, but they look very different.

These things are typically used for large arrays of luminaires inside large industrial, retail, or warehouse buildings, as well as outdoor lighting on such buildings. The ones with multiple circuits can handle both chores simultaneously quite well. I've also used them for break buzzers in manufacturing settings. The programming is tedious but very powerful.