Abacus is an NFT valuation system on Arbitrum that uses optimistic proof-of-stake to create a liquid backed valuation system.
Traders act as validators by staking their money in different valuation tranches. The attributable valuation of the NFT is the liquidity locked in the pool at any point in time. Validators are kept honest because if a pool closes, the liquidity in the pool is sent to the NFT owner and the pool receives the proceeds of an immediate NFT auction which is then liquidated in a FIFO manner based on tranche positioning.
Due to the immediate closure ability, the project assumes that the valuation is 100% accurate as is done with optimistic roll-ups.