Martin Brenner's, Pilot Balloon Resources 

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Met. Office Pilot Balloon Slide Rule MK V

This is a Mark V Pilot Balloon Slide Rule  The printed scales are engraved in the plastic faces. The slide rule has 4 captive cursors (Plexiglas windows and brass guides) that ride in slots on the top and bottom edges. Each can be moved independently of one another. Brass knobs at both ends of the slide facilitate its movement.  This rule was used by the CBM (Commonwealth Bureau of Meteorology and does not have a Met Office Stamp and date.   

This slide rule contains a engraved notation directing the user to see a not on the back of the rule however no note was engraved on the back of the rule.  I believe that the annotation is a carryover from the Mark IV.A rule but the note about graticule line spacing note was not specified for this model, hence the note on back of rule label was omitted in error.   The more recent Mark 5 rule includes the note on the back but not the reference to it on the front.    

 A large image showing the scales of the Mark V slide rule is also posted.  This rule is very similar to the Mark IV.A rule and it is manufactured by the same manufacturer however the scales lack the horizontal lines for a cleaner look.  Some changes in the fiducial marks are also incorporated.