What size staples does the swing line electric stapler model 34201 use?

I had the same problem. I went to a Sears Hardware store. They did not have Swingline staplers and did not know, so I guessed. I brought it home and used it. It worked.

I purchased a box of Craftsman Wire Staples #974458. It indicated that it was for use with Craftsman, Duo-Fast and Black and Decker Cobra Manual and Electric Staplers. More important they are described as Heavy-Duty Wide Crown 5/16-in. Wire Staples