The Tektronix Type 1L10 is a high-frequency spectrum analyzer plug-in for 500-series scopes, covering 1 MHz to 36 MHz.
Like the Type 1L5, its resolution bandwidth is 10 Hz to 2 kHz.
It was introduced in 1965 and was Tek's first spectrum
analyzer – other early analyzer plug-ins were OEM'ed from Pentrix.
(The L-10A might have preceded the 1L10.)
The 1L10 was sold through 1971 or 1972.