My system:
Every item is photographed, inventoried, boxed and labelled. Original factory boxes, paperwork and packaging is retained for all models (large and small). External protective "packing" boxes are used for everything. All boxes have a color coded label for easy identification. Instruction sheets are filed in a 3 ring binder for future reference.
A "catalog" page is maintained on my computer for every item. Examples attached.
Photos of the external "packing" boxes are given a file name and stored on my computer. To locate a boxed item by file name I use the computer "search" function.