Tekron has sold two different antenna's over the years. The first antenna, pictured below is the Panasonic VIC 100 NAIS Antenna. This antenna is only capable of receiving a GPS signal and was sold with the TCG 01, TCG 01-E, TCG 02-E, NTS 01 and the TTM 01-E.
When Tekron introduced multi-constallation on the TCG G series clocks, a new antenna was required which support both the GLONASS and GPS bands. Tekron switched to the Tallysman TW3470 antenna picture below. The Tallysman antenna has a less conical shape to it and the two antennas are mounted differently.
If your system has the NIAS GPS only antenna, then you can still use this with our modern products. However, you will be limited to only receiving GPS satellites.