I have an inventory of all pieces I have and have had it since the beginning. I have several individual files listed by area(Southeast, Northeast, Gulf, Great Lakes, Western, Society/Christmas and Misc.). I list the pieces in each catagory alpabetically and include HL number, name, serial number, edition size, issue date, retired date, retail price, actual cost, secondary market price and where the box is stored in my box storage area. I also include whether the piece is signed and any special information about the piece such as "green water", Canadian, lightning rod, etc. I have a hard copy that I keep at my desk and keep the files on hard drive with a CD for backup. I also include on the bottom of each section a totals list for retail,actual and secondary costs. It helps me and also serves as information for my wife in case some unforseen incident should happen. That way if she should want to sell she has an idea of the value. Sort of like an additional insurance policy. Works for me!