Three monocular microscopes Three monocular microscopes. Numbering runs as follows RCSI/M/31a to RCSI/M/31c. Made by Ernst Leitz Wetzlar. The engraving on the neck of 31a reads 'RCSI no. 3', that on 31b reads 'RCSI no. 31' and that on 31c reads 'RCSI no. 28'. Undated