The upper case JPG signifies the file is 8 bit. This is unusual as when I had an 8 bit computer in 1994 the only image files were .BMP and .TIF. I am currently having some problems with .jpgs not opening in the stock photo app in Windows 10 but if I select edit first and display them, then then do open. Naturally, I have files that once were 16 bit, some 32 bit and now my file system and all working programs are 64 bit. Were you around when "long file names" became possible in Windows 95 in yes, 1995. I don't know about Apple. Until then all of the file names also were all caps. I truly appreciate the work of those who labor to keep legacy legible.