#55 Coleman Orifice S1-02921182255
Coleman burner orifice, size 55 or 0.052. Length of orifice is 7/8". Typical found in high-efficiency LP furnaces. Thread size is a 3/8" fine.
Known as part numbers S1-02921182255, 029-21182-255, 02921182055 & 029-21182-055.