85 and down for mechanical speedos.
There's an adjuster deep, deep within the innards of the thing that is used to calibrate the gauge via the amount of tension the clock spring has. Likely somethng you really don't want to frig with unless you've got uber confidencein your bezel removal and clockworks skills.
Someone had a nice writeup with pix (Wille R. IIRC) on how to do it on the older version gauges, but I'm not sure if it applies exactly to the Jaeger gauges the S3's have.
That being said, one 'could' pop the bezel and glass then run the indicator needle around full clockwise then very carefully trip the tip of it over the stop pin down by 10mph so that its basically wound one rotation tighter.
Whether it would be right, (prolly not), or the needle would break, (good probability), or any number of other not so good type scenarios, if nothing else it will indeed cause the needle to read slower (possibly way too much so even)
IIRC Palo Alto are the folks to talk to about getting things properly tuned in mechanical gauge heads if you want to farm it out to someplace that has the right tools and such.