A commercial edging machine ??

Just a guess but could be a little Mantis tiller with the edging attachment.

Thanks !!!

Peter

I use a Weedeater turned on its side and walk backwards. With a steady hand, you can get a perfect looking edge. I learned this from watching professional landscapers. No need to buy a separate edging machine--why maintain another gas-powered machine?

I use a string trimmer for edging/grooming too, along my driveway and walkways, but it's not going to dig down 5" and pile earth into a mound, in fact any earth it dislodges is flung far and wide. It sounds to me from what the OP describes is that initially a small tiller was used (or dug by hand) and then the sod edge maintained with a string trimmer. However with regular/constant use over a couple of years a string trimmer alone will eventually create a fairly large bevel/champher at a lawn edge, but still the soil removed will not create a mound, it will be flung away. And by creating such a deep champher too much root at the edge of the sod will be exposed to the point that the edge will begin to die back and look awful, so not a very smart practice... often lawn service crews will strive to create a large champer where the sod meets a bed or a curb, they try to create a dead space at as many borders as possible in order to make their mowing easier and faster.