Abstract: In order to that optically readable small code marks can be correctly read by a reader, an optically readable code mark 15 is marked on an surgical instrument 14 at an optional location by using a laser, the code mark being in the form of recesses and projections which are apparently different in magnitude from roughness of the instrument surface at that location. Thus, the code mark is marked on the surgical instrument itself by laser marking and is optically read, resulting in correct reading of the mark and a considerable improvement in durability of the mark.

Abstract: A vertical pump (1) having a single or plurality of helical blades (10, 11, 12) mounted on a forward end of a rotary drive shaft (2) of the pump. The pump is of nonblocked type in which the helical blade or blades (10, 11, 12) are disposed with superior balance with respect to the rotary drive shaft (2), and is wide in flow passage between blade portions of the helical blades. The pump is particularly suitable for sewage treatment or the like.