Red box = CPO (Certified Pre Owned). Some of them were never issued and they just get inspected by Sig and shipped out as CPO. Others had heavier use and get refinished, inspected, springs replaced, etc. and then get shipped out as CPO.
I'm sure someone will be along to tell you what you can look for to know if it's been refinished, if you're curious.
What JBird679 stated is true. The CPO (Certified Pre Owned) guns may be used & reconditioned to un-used over runs. Post some pics and show the first half of the serial number if you want more details about your acquisition and congrats.
This serial numbered frame (lower) would be German manufactured in the early 2000's and as for the slide, Sig started using the long extractor on some of their slides around 2009 and they are currently still using them. Having said that, CPO pistols are a good value and should serve you well. Enjoy your new acquisition.
