I looked again at the bobbins my Aunt gave me. All of them have the letter L either printed or imbedded on one side of the cardboard. Only have 1 with white thread and it has the number 40 printed on the opposite side of the cardboard. The dark gray thread has THREADS and USA imbedded on the opposite side of the cardboard. The brown thread has ATCO printed on the same side as the L and on the reverse side is SPUN 50 DEE and what I think is a trademark -- a star with a circle around it. There is more red printing around the trademark and I can't determine what it represents. I know in my lifetime (78 years) I've seen thread with a star as part of its trademark.