Defecto Antesto

I live at 5900 feet, but I ride exclusively at sea level (Glamis!). I want to test my compression here in the mountains, but I would like to be able to estimate what my compression will be at sea level where I ride. Does anyone know an equation that would allow me to convert my high-altitude compression numbers to a sea-level estimate? I'm pretty ignorant about air density, specific volume, etc., and how it all works together. Any help greatly appreciated.

Hey all. I bought this set of stainless front brake lines in 1997 or so. I am now trying to figure out what brand they are so I can pick up a matching rear line (yes, I know I should have considered this a dozen years ago). I can't find a similar looking line on the internet, so I am hoping somebody on this board might be able to identify it for me. Pic below. Thanks in advance for any suggestions.