Detailed doppler measurements show that AMSAT-OSCAR 91 (AO 91) is object 43017, 2017-073E.
There is a small frequency drift on the downlink of OSCAR 91. During ascending passes, i.e. early afternoon passes from south to north, with the satellite in full sunlight, the downlink shows a frequency drift of about -19 Hz per minute.
73, Nico PA0DLO