I don't think it was ground.

Looks more like a Maldive Termite bite to me.

 

I ask myself how much expensive is the right resistor, and how much expensive is that job...

 

But it makes your otherwise poor investment into 10,000 43 ohm 2 watt resistors suddenly useful.

 

this is an old school method of increasing resistance. should have been doped/painted afterward.

What would be the reason for this:
[ed]
updated photo for clairity

[/ed]

It is the best shot I could get, sorry about the blur..why would you grind away a resistor? is it because the manufacture bought the wrong resistors and edited these to make them work?

It looks bad in the photo, but it is "perfectly" ground. Not "blown". no traces of heat or damage other than intentional.

 

This is an old idea. Note that it will only work on carbon composition resistors. After grinding put a drop of epoxy cement on to seal it. The resulting resistor will have a much lower power rating, and will be much weaker in strength. If you try to remove it from the board, it will probably break in two.

 

From a product description for this item:

The Dial-A-Temp offers easy control of fan speed and noise with plug-in versatility, no tools required. These are great for controlling woodstove blowers. Rated for light motor loads up to 3 amps, this control can increase the usefulness of all types of fans and blowers. This is a rugged flame-retardant thermoplastic casing outside; UL recognized components and solid state construction inside. Plug in your fan to the Dial-A-Temp then plug it into the wall (three prong plug). Adjust the knob for fan speed. Measures 3"H x 2"W.

Well, it better be flame retardant.

 

It says UL recognized! Must have been recognized in the FAIL category!!

 

ROFLMAOF!!!!!!!!!!!
I can't take it any more.........

 

This is the geek equivalent of a traffic accident. You try not to look,but can't help yourself.