this is a masterlock my friend gave me. it looks like its splattered with black paint to look rugged but it opens in 2 seconds from the looks of it, it looks like a ML No.3 but i know that a couple of them look very similar. sorry for the bad pics, used my webcam and the pictures reversed when i saved them, dont know why
Thats their rust-oleum (thats how they spell it i think) coating. It keeps it from rusting. other than that its just a regular 4-pin master as you have discovered. The shackle length probably gives away the #.
Master Lock No Rust Rust-oleum Finish 1-1/2 In. Hardened Steel Shackle the lock body won't rust, 1-1/2 extra inch long shackle is manufactured from hardened steel it's has 4 pin cylinder hope this help thanks
from the looks of it, it looks like a ML No.3 but i know that a couple of them look very similar. sorry for the bad pics, used my webcam and the pictures reversed when i saved them, dont know why 
