2N1540 semiconductor manufactured by Sylvania, listed as 2N1540 (circa 1979).

2N1539A semiconductor manufactured by Sylvania, listed as 2N1539A (circa 1979).

2N1539 semiconductor manufactured by Sylvania, listed as 2N1539 (circa 1979).

2N1538A semiconductor manufactured by Sylvania, listed as 2N1538A (circa 1979).

2N1538 semiconductor manufactured by Sylvania, listed as 2N1538 (circa 1979).

2N1537A semiconductor manufactured by Sylvania, listed as 2N1537A (circa 1979).

2N1537 semiconductor manufactured by Sylvania, listed as 2N1537 (circa 1979).

2N1536A semiconductor manufactured by Sylvania, listed as 2N1536A (circa 1979).

2N1536 semiconductor manufactured by Sylvania, listed as 2N1536 (circa 1979).

2N1535B semiconductor manufactured by Sylvania, listed as 2N1535B (circa 1979).

2N1535A semiconductor manufactured by Sylvania, listed as 2N1535A (circa 1979).

2N1535 semiconductor manufactured by Sylvania, listed as 2N1535 (circa 1979).

2N1534A semiconductor manufactured by Sylvania, listed as 2N1534A (circa 1979).

2N1534 semiconductor manufactured by Sylvania, listed as 2N1534 (circa 1979).

2N1533 semiconductor manufactured by Sylvania, listed as 2N1533 (circa 1979).

2N1532A semiconductor manufactured by Sylvania, listed as 2N1532A (circa 1979).

2N1532 semiconductor manufactured by Sylvania, listed as 2N1532 (circa 1979).

2N1531A semiconductor manufactured by Sylvania, listed as 2N1531A (circa 1979).

2N1531 semiconductor manufactured by Sylvania, listed as 2N1531 (circa 1979).

2N1530A semiconductor manufactured by Sylvania, listed as 2N1530A (circa 1979).