I had a Police 3 for a while, but I didn’t like at all how the tip had such a large drop added to it. All the previous models had that perfect splinter picker tip (that unsuspecting people can break off, hence the drop added to the Police 3), so I didn’t like that. I also had Tom Krein regrind that one to make it thinner and pointier, but to me I generally like a little more belly to the blade and I ended up selling it.
The Police 4 on the other hand added significant belly to the edge, a much less dropped tip, and K390 which I had never tried before. I’ve really liked this knife from day one all around, including the ergonomics. I’m a nut for thin edges though since I really value performance over durability, so I was able to convince Tom to help me out and regrind the Police 4 recently. He’s done probably. 35-45 over the last 17 or so years for me. He’s so in demand for his great customs though that he is very selective on how many, and which particular knives he will regrind these days so I don’t ask often. If you PM me I can give you a little more information if you want. Tom is really good at grinding to very thin edges without overheating the steel and impacting the heat treat. I know that K390 is a belt killer, so the regrinds are probably more than you you would think. I know there are knifemakers offering their services for regrinds and can do a fine job. As long as you look for others that have actually used their knives after the regrinds and are happy with the steel’s edge performance then you can be pretty sure you will be happy with the results of any particular knifemaker.