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OSUFlatland
I know they bought Atmel a while back, but have no idea how compatible the interfaces are.
This one likely works. AFAIK there is only one such device for the whole AVR range.
Looks like an STK500, which is up to 64k, only, so no bootloader programming possible. STK500v2 is good.
Socket has only 28 pins.
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OSUFlatland
Also, I see no ISP header on my Sanguinololu, so I assume I'll need an external programmer.
It's the 6-pin header at the bottom right corner: [reprap.org] In case your programmer has a 10 pin connector, place it in a way that two pins on each side are left unconnected.
There's no danger with trying. It's possible to brick ATmegas (disable serial programming or setting it to external clock instead of external oscillator), but to do so, the programmer has to work. The wiki page for Gen7 Arduino IDE Support describes how all this works and this package its self has the required bootloader binaries inside.