The long, thin spring-loaded metal flap labeled the "paper conductor" on the SM3 and SM4 and labeled the "erasing table" on the SM2 are all the same part. They serve a few functions.

They can be used for erasing mistakes certainly and help to keep dust and debris from going into the carriage and rollers.

The "paper conductor" description sounds like a fun translation of something from German into English, but this part also prevents the paper which goes under the paper bail and forces it up and back to the paper table and the paper support. Presumably without it, a slightly curved piece of paper might be misrouted to go right back into the platen a second time as the paper advances.

This sort of paper conductor/dust shield can also be found on some later 1960s+ Smith-Corona (SCM) machines. For example, see the Galaxie II which calls that part the erasure table.

Step-by-Step Tutorial: How to Use an Olympia SM4, SM3, or SM2 typewriter - Works for SM1 & SM5. by [[Mr and Mrs Vintage Typewriter]]

Olympia SM-3 SM-4 Typewriter Carriage Binding, Repair, Replace Body Spacers Tutorial Demo by [[Phoenix Typewriter]]

The SM3 and SM4

Subtle differences between the two models.