Fred, Sybelle Jargstorf's books may shed some clarification, but mine are lost in storage at this time. "Glass Beads From Europe", I believe, shows the "surfboards" and I'm quite sure they are 1920s items. The elbow shape predates those, but how many years, I don't know - and they are a more versatile shape than the tabular "surfboards". Five or seven elbows, matching, make great focals for a short necklace.