nprofile1qyt8wumn8ghj7un9d3shjtnyd968gmewwp6kytcqyzmkfwycmmes47883xat2d429zqartc54gjrp7vdnrnp6fr8kamnyhgu0v7 (nprofile…u0v7) … When specifying the short form dates for such items, I will often write something like “c.1924[?]” – with the question mark in brackets but not the date, to indicate the date is present but just not obviously the publication date. (As opposed to something like “[c.1924?]” – with the date and the question mark in brackets, for things where that date doesn’t actually appear anywhere.)
This is my own made-up syntax though. I should probably read more about proper bibliography.