Richard,
Your post about the file sure stopped me cold. I have every Brownell's catalogue from 1979 up to 2005 and I read them line for line when I receive them. When I read your post I thought "Boy, I wouldn't have missed that", so I spent a couple of hours leafing through '79 to '87. There is no such file listed that I can find. There is listed, on the same page as the sights, as you said, a 3-square sight file. These have parallel sides, 2 safe sides, and 60 degree included angles. They are for filing dovetail slots in barrels, etc. I wonder if this is the file you were thinking of. A file for cutting the shallow-V rear sights, for dangerous game rifles, would have an included angle of 120 to 130 degrees.