Socked on the nose ("SON"), also called Bullseye cancel, in philately, refers to a cancellation of a postage stamp in which the postmark, typically a circle with the date and town name where mailed, has been applied centered on the stamp. [1][2] The ideal SON has the entire postmark inside the margins, although this is not always possible, because the stamp may be too small or the postmark too large.
Some philatelists and collectors of cancellations have a special interest in, prefer, and/or collect SON mainly because the date, time, and place the stamp was used, or postmarked, can be identified by the cancellation. This allows specialised collectors to collect, for example, all of the postmarks of a particular country, state, city, county, date range, etc., without collecting entire covers.[3]
Because modern machine cancellations are normally arranged so that the "wavy lines", slogans, or other killers are applied to the stamp, leaving the postmark clear, dealers and collectors desiring SONs will position the stamp on the cover so as to fall under the postmark.[4]
The term Bull's Eye also is used for the first stamps of Brazil.