Posted accidentally (I'm not sure how). You may disregard.
(Message edited by steve_jelf_parkerfield_ks on June 20, 2018)
It is a good question.
And the same question is relevant to headlight focus adjustment on generator cars with the new run of retro headlight bulbs from the vendors many have the bulb filament vertical rather than horizontal when installed in a stock Model T headlight socket. To correct this problem so You can focus the headlights you need to drill a new hole in the headlight can so the socket can be turned 90 degrees which line up the bulb correctly for horizontal filaments. I was looking at a model T generator car the other day and when the lights were switched from high to low beam You could not see any difference in light spread only a slight change in brilliance indicating they may have had the wrong bulbs with vertical elements which can not be focused ?