If you pick up Stanley planes in junk shops and wonder how old they are, I have a suggestion. Print out this web page and carry it with you. It’s a dichotomous key: Answer a few yes/no questions about the tool to discover its date. You might find a Type 1 (1867-1869), worth a lot of money to an obsessed Stanley collector.
I’m not obsessed, but I did check the six bench planes in my toolbox. Two were Type 14 (1929-30), three were Type 15 (1931-32). That’s odd, I would have expected a greater spread of dates.