The Southern Pacific had several different switch cuts for various functions. I believe this was for the SP CS 5 switch locks. Being marked SP Lines a little more harder and desirable to obtain than the SP CS 5 keys. Front has SP LINES CS 5. Key has seen use with all letters still legible. The letters C&S before the 5 are more worn. But still can be seen. Back side has the Smaller left sided Adlake. Key also has the nice smooth pocket worn finish. Could be an up grade for your Southern Pacific CS 5 key. BB
