SUDDENLY REALIZED If you take away some lines and round the corner a bit: it perfectly looks like katakana ア and still is superimposed J and P! Or could be like this, I guess more clearly recognizable as JP. (Sorry for unprofessional collaging, I know it.)

According to Wikipedia, the correct name of “山手線” is “やまのてせん.” In the application form of business license submitted by The National Railway (then 日本国有鉄道) to the government before the start of operation in early Meiji era, it was indicated as “山ノ手線,” and remained so until / during the World War I...