Yup... That is an AT psu.
A couple of hints:
You can allways mount an ATX psu inside an AT case, it just need to be mounted on it's head. (upside-down).
If the ATX psu is in good shape and has -5volt (white wire), you can buy a cheap ATX-AT converter on eBay.
If the ATX PSU do not have -5volt, then you can buy a converter that are not too expensive though not cheap.
This, more expensive one, has a converter on it that gives you -5volt output.
The power button on any AT case, are designed for 110/220 volt, though they can handle low volt as well.
EDIT:
The best you can do, if you are 110 percent paranoid about PSU's blowing up, is to purchase a decent good
quality ATX psu wich are brand new, and buy that converter with -5volt generator on it.
Don't eat stuff off a 15 year old never cleaned cpu cooler.
Those cakes make you sick....
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