Might be the original ballast if it's a newer fixture. I find the box stores here don't stock LPF ballast even during the magnetic days. In fact my local HD sells a bunch of HPF F20 ballasts.
I was also thinking that stores didn't stock these even in the 90s and 2000s when magnetic ballasts were still plentiful but I'm certain it's not original since another identical Sears shoplight I got a couple years ago has a full-power GE Bonusline ballast! Another one had a (half-dead) Universal Therm-O-Matic I installed in my 3-lamp fixture for the center lamp. The other light from the same place as the one pictured above is also a Sears and has a US Fluorescent NPF ballast. Also, you can see where the larger HPF ballast once was by heat marks...
Can you post a pic of the inside of the fixture surrounding the ballast? I agree with Joe that this is probably the orignal ballast unless you can see that there are other screw holes that are used (worn paint).
I can totally see other holes were used...hold on I will post a pic
BTW this is being mercury-migration tested!
I took a pic of it's identical mate who has the same thing going on and you can see less dust and dirt under where the original ballast would have been a well as scratch marks in the paint.
If the holes appear used them it is a replacement ballast but you never mentioned that before so I assumed they didn't appear used. Time to put a nice HPF ballast in!
That was my thought too! I don't have any and I'll use this till it dies but then it will either have a HPF (preferably full power) ballast or an electronic one at least...
Yeah I know! Actually I feel like I see these do strange and scary things when they finally DO fail! I had an Advance Benchlite one fail by first only lighting the cathodes, then it developed a nasty buzzing and would draw MUCH more current than it was rated for and get HOT! And there's that one I have that seems to have internally shunted itself for one lamp!
Yeah I snipped the wires off the Benchlite ballast and threw it out. I said I was going to keep it to shut everyone up on the LG. I will make good use of the wires though since I can't find 18 AWG solid wire were, which is so necessary for fluorescent lights.
I used some stranded #16 for the shunted ballast in the 3-lamp troffer I have...(The wires were too short). It's a rat's nest in there admittedly, as are many of my own wiring jobs for my own lights...
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BTW this is being mercury-migration tested!
I took a pic of it's identical mate who has the same thing going on and you can see less dust and dirt under where the original ballast would have been a well as scratch marks in the paint.