The Tektronix 017-012 is a 50 Ω "Transformer-matched T" (power splitter) with GR-874 connectors on short coax pigtails. The rise time is specified to be less than 500 ps.
The 1964 catalog says:
This unit provides two 50-ohm outputs from one 50-ohm input
and divides the regenerated trigger for simultaneous triggering
of two sampling-sweep systems.
Order Part Number 017-012 $45