This is a Olympus MSPlan 20x metallurgical microscope objective.  N.A. 0.46 F=180

Bausch & Lomb 20x Phase Objective 0.50 N.A.   Flat Field 0.18mm Cover Glass

Olympus UVFL 20x Objective 160mm Tube Length 0.17mm Cover Glass N.A. 0.65 Catalog #:  101726  

Leica Achro 20x Objective for GALEN III 160mm Tube Length N.A. 0.40   Cover Slip Thickness 0.17 Leica Catalog Number:   13317518

Olympus NeoDPlan 20x Metallurgical Objective Infinity Corrected N.A. 0.40 Focal Length 180mm Olympus Catalog Number:  103815 Marked IC 20

Nikon BD Plan 20x Objective 20x N.A. 0.4 Focal Length:  210 Nikon Catalog Number:   320231

Leitz Plan 20x Objective Plan 20x Tube Length:  160mm N.A.  0.45 Leitz Catalog Number:  519865

Bausch & Lomb 20x B.F. / D.F. Metallugerical Objective   20x Bright Field  /  Dark Field PlanAchromat Metallurgical N.A.:  0.40 No Cover Glass  /  Slip

Bausch & Lomb / B&L K20x Eyepiece

Olympus K20x Eyepiece Bi

AO 20x Plan Achro Objective 20x Plan Achro N.A.: 0.50 Infinity Corrected Made in USA AO Catalog Number:  1022

American Optical / AO 20x Plan Achromat Objective Infinity Corrected N.A.:  0.50 Plan Acro Made in USA AO Catalog Number:  1022

Bausch & Lomb 20x Plan Objective Plan 20x N.A.: 0.40 160mm Tube Length 0.17 mm Cover Slip Thickness

Leica 20x LWD Phase Achromat Objective W/ Correction Collar 20x Long Working Distance Phase  Achromat  N.A.:  0.50 Correction Collar: 0.5-1.5mm Leica (reichert / ao) Catalog Number:  1217A

Nikon 20x Focusing Eyepiece 20x 12.5mm Field of View

Olympus 20x Plan Phase Objective 20x Plan Phase Contrast:  PH1 Infinity Corrected N.A.:  0.40

Nikon 20x Objective Hoffman Modulation Contrast 20x Hoffman Modulation Contrast N.A.:  0.40 Tube Length:  160mm Nikon Catalog Number:  100789

Leitz Pv 20x Phase Contrast Objective PV 20x N.A.:  0.35 Leitz Catalog Number:  D 17781

Leitz 20x UM Iris Diaphragm Objective 20x Iris Diaphragm N.A.:  0.33  

Leitz Plan 20x Objective  Leitz Plan 20x Tube Length:  160mm N.A.:  0.45 Leitz Catalog Number:  519865

Leitz Pv / Phase  20x Objective  #: D-21901 Leitz Pv / Phase Objective 20x Tube Length:  170mm N.A.:  0.45 Leitz Catalog Number:  D-21901

Leitz 20x PV n Objective 20x PV n Tube Length:  170mm N.A.:   0.45 Leitz Catalog Number:  D 21901

Leitz 20x UM3 20x UM3 Iris Diaphgram  

Wild-20x Eyepiece

Wild 20x Focusing Eyepiece 13mm Field Of View

AO-20x Infinity Corrected Phase Contrast Objective    #:  1235 Infinity Corrected N.A.:    0.50 Bright Phase Contrast American Optical Catalog Number:   1235

Olympus 20x LCAch Infinity-Corrected  PhC Phase Contrast Objective Infinity Corrected N.A.:  0.40

AO Spencer 20x Brightfield Phase-Contrast Objective Brightfield Phase Contrast N.A.:   0.50

Olympus 20x LWD C A20 PL T6 Objective Phase Contrast Objective Tube Length:  160mm N.A.:  0.40

Zeiss 20x 8.3mm JENA Objective 20x 8.3 mm N.A.:  0.65