Ironically the older 4" Heavy Barrel Round Butt 10's are a little harder to find, but all the M10's from the 10-11 on up are all HB RB's

The 10-8 in the pic was made in 1980, was probably an ex-LEO gun but may have been a security gun. The seller didn't know where it came from.

In my experience security guns get beat up a lot worse than LEO guns. Like was said above, most times issue guns were inspected and most private purchase guns were maintained by the LEO. Even issue LEO guns were carried by one, maybe two or three officers during their service lives. Security guns are carried by several dozens of people, sometimes several different people in one day, and are treated with little more regard than a flashlight by the people carrying them. There is no incentive to care about a gun that is never inspected, doesn't belong to you,is rarely if ever fired, and chances are in a year you won't be working there anyway.

When I was a rent-a-cop we actually fired our Glock 22's 4 times a year, and were required to clean them before we could leave the range area. But I worked for Wackenhut, which is a multi-billion dollar corporation that paid well and was hard to get into.....so abusing weapons was not good for one's employment status....... The $8 an hour armed guards at Jelly Donut Security LLC who employ 40 people, with a revolving door employee retention, probably aren't as stringent with weapons maintenance or qualifications.