File naming:

19_x.s1p: First JLCPCB Board
20_x.s1p: First OSHPARK Board
40_xc.s1p: Second JLCPCB Board with DL-SMA-K513-08K SMA Connectors
40_xu.s1p: Second JLCPCB Board with CON-SMA-EDGE-S SMA Connectors
41_xc.s1p: Second OSHPARK Board with DL-SMA-K513-08K SMA Connectors
41_xu.s1p: Second OSHPARK Board with CON-SMA-EDGE-S SMA Connectors
sim.s1p: Simulation of 1pF discontinuities matching a transmission line length on the first JLC board.

x is a number between 1 and 4 corresponding to the trace on each board being measured. 1 is the northmost trace on the board and 4 is the southmost board on the board.

u stands for UK (the country of the manufacturer of CON-SMA-EDGE-S).
c stands for China (the country of the manufacturer of DL-SMA-K513-08K).