Oh nice! Does it have an SR 000 code on the metal tab inside the neck near the base? If so, that makes it pre-1994. When OSRAM took over the tab's code was different.
Hmm, on one of my Sylvania mercs, there's tag with the SR 008 on it but the other one has SR 03 on the stem press instead. Anyway SR 109 should be either Jan 1980 or Jan 1990.