I built a free Lesney 1-75 collection album: no account, nothing stored on my end
I collect Lesney-era Matchbox and wanted something better than a spreadsheet, so I made a Panini-style album for it: matchbox-collection.com
421 slots, one per casting, covering the 1-75 from 1953 to 1975 plus Super Kings, Speed Kings, Battle Kings, Sky Busters and Yesteryear. Free, no sign-up, no ads. Your collection lives in your browser's storage, not on a server. You export a JSON file to back it up or move devices.
Each specimen records its box type (A through M) and the album flags it if that box type wasn't in use while the casting held its number, which is the classic way people end up with a mismatched box. You can also store all the models of the casting you have.
Built by one person so any corrections/improvements are very welcome. I hope it can be useful for you.