Hey everyone,
Thanks for this thread. I'm actually in a similar situation as the OP as I purchased an Elmo 1012s-XL off of eBay and the filter selection switch is completely missing.
On mine it appears the built-in filter is in the "ON" position, because when I push the metal button on the inside of the camera where the cartridge goes I can see it moving out of position when held against the light. It also moves out of position when I insert the test roll I bought, a Pro8mm roll of 500 ASA Daylight balanced film. Considering I plan on shooting only in daylight or under daylight balanced indoor bulbs, I'm guessing the color will be fine because the cartridge moves the filter out of the way.
Is my thinking correct?