There are SOOO many different numbers that BM makes that I have become numb to even trying to understand them, so it's when my friend at Ashokan had his 5000 that I got excited about this knife, but I didn't want the auto version so I had to dig a little to see what a manual version was numbered as and went from there, New Graham Knives did me very well and had the knife to me in as little as two days once the order was placed, I called late in the day but they went the extra effort to make sure it started it's journey to me that night, thanks again guys!
As to the scales, there is that concern, in fact the 5000 auto I got to play with had some scratches here and there but nothing too bad, I figure riding in the sheath will help a lot in that matter, glad I did make it to fit the clip as when I go to Church I can't wear the sheath but slip the knife into my pocket, never know when you'll need a good strong knife, nothing like saying "gee I have one at home"
I did get a Skirmish and that dwarfs this knife considerably!

But won't replace it, the Skirmish is more for show for me and with it's over 4" blade length makes it a little more trouble if you get caught carrying it in about any state except maybe California, where I hear that any length blade on a folder is ok as long as it's not double edged or an automatic.
The sheath carry works well, it is a hard draw out of it's home, let me tell ya! But has a really nice pop when it goes back in, never to fall out with that guard area like it has. It still digs a little bit of leather so it's still working a place in the sheath but that will calm down a bit.
The 520 is hard to beat with the flat grind and high grind line, this knife will push cut like none I've owned with the exception of maybe a Jimmy Fikes Cabin Boy chiseleged knife

G2