See-through computer display systems

A head-worn computer including a frame with see-through display optics and a removable combiner comprising:

• a. a combiner that is partially reflective;
• b. two or more parallel pins, made from a magnetic material, that are rigidly attached to the combiner;
• c. magnets attached to a frame of the head-worn computer in positions that correspond to the pins, that attract the pins so that the pins slide into matching bores in the frame to position the combiner below the frame;
• and
• d. wherein the strength of the magnets is selected to be strong enough to hold the combiner in position during use but weak enough to enable the combiner to be removed.