2N1550 semiconductor manufactured by Sylvania, listed as 2N1550 (circa 1979).

2N1549A semiconductor manufactured by Sylvania, listed as 2N1549A (circa 1979).

2N1549 semiconductor manufactured by Sylvania, listed as 2N1549 (circa 1979).

2N1548A semiconductor manufactured by Sylvania, listed as 2N1548A (circa 1979).

2N1548 semiconductor manufactured by Sylvania, listed as 2N1548 (circa 1979).

2N1547A semiconductor manufactured by Sylvania, listed as 2N1547A (circa 1979).

2N1547 semiconductor manufactured by Sylvania, listed as 2N1547 (circa 1979).

2N1546A semiconductor manufactured by Sylvania, listed as 2N1546A (circa 1979).

2N1546 semiconductor manufactured by Sylvania, listed as 2N1546 (circa 1979).

2N1545A semiconductor manufactured by Sylvania, listed as 2N1545A (circa 1979).

2N1545 semiconductor manufactured by Sylvania, listed as 2N1545 (circa 1979).

2N1544A semiconductor manufactured by Sylvania, listed as 2N1544A (circa 1979).

2N1544 semiconductor manufactured by Sylvania, listed as 2N1544 (circa 1979).

2N1543A semiconductor manufactured by Sylvania, listed as 2N1543A (circa 1979).

2N1543 semiconductor manufactured by Sylvania, listed as 2N1543 (circa 1979).

2N1542A semiconductor manufactured by Sylvania, listed as 2N1542A (circa 1979).

2N1542 semiconductor manufactured by Sylvania, listed as 2N1542 (circa 1979).

2N1541A semiconductor manufactured by Sylvania, listed as 2N1541A (circa 1979).

2N1541 semiconductor manufactured by Sylvania, listed as 2N1541 (circa 1979).

2N1540A semiconductor manufactured by Sylvania, listed as 2N1540A (circa 1979).