Shelf for a typewriter. Manual typewriters are heavy, the springs help move the shelf up and down. Once you move your shelf to the top, turn that thumb latch to lock it in place.
Some examples:
https://instappraisal.com/appraisal/antique-secretary-desk-slide-out-typewriter-shelf
https://www.myantiquefurniturecollection.com/i-have-a-vintage-myrtle-desk-co.with-pop-up-typewriter-shelf-awesome-two-…-53793.html
https://shop.blackdogsalvage.com/tanker-desk-with-build-in-typewriter/
https://www.ebay.com/itm/274785544688
This was so much like the wrestling promos/interviews I watched long ago I kept seeing a stone faced Mean Gene Okerlund holding a mic up to Lindell. It has the same disjointed intensity. Surreal.