I’m using it, in the beginning a lot, and once you start remembering the differences and nuances stated in the e book, i’we been using it on occasion “on the fly”. I can truly recommend it to everyone.
The book has more detail but I really love the e book, it very quickly helps identify part variants and tells you whether or not they go together. Not nearly as heavy as the book.
The app is just an identification tool. There is no exhaustive information about the models nor their particularities. If you have the book and are using it frequently, you won’t need the app to identify a Speedmaster...
I bought it back then, but honestly I can’t remember when I used it last time to identify a Speedmaster 😟