Copy the complete model marking
Use the identifier printed on the product label. Keep hyphens and suffixes in your own record so you can compare the unit with the models named on the document cover. Do not substitute a serial number for a model name.
Follow the official source
Go to Sony support, search for the model, and inspect its manuals section. For example, the D-151 support page lists a user guide. A document upload date is not necessarily the product’s launch date.
Save a traceable note
Record the document title, source URL, language and any listed revision. If a manual covers several products, check which instructions apply to yours. Keep a local copy where its license and terms permit, and link to the official source when sharing your collection notes.