"T"3 GM used T3 bulbs from 1956-1971 on their two and four lamp cars & trucks.
I always get excited when I come across an original T3 lamp and always try and date it. Yes you can date T3's.
This one is a 2-12 volt (two lamp system 7" diameter) so it's a high/low beam.
This bulb was used from 1959-1969. The clue here is the "lines" in the T3 Triangle and the small 12V under the 2.