https://www.rfwiz.com/comtelco-a1843b-70-base-load?tag=uhf&page=5
A1843B-70 Comtelco UHF 470-490 MHz 3dBd Gain 5/8 Wave 21" Base Load BLACK finish Mobile Antenna
Comtelco's A1843B-70 470-490 MHz UHF 21 inch 5/8 Wave 3dBd Gain Black Base Load Mobile Antenna Information and specifications page