Hey, I’ve added the block number tag to CAIP-19:
- CAIP-19: Add block number tag by TimDaub · Pull Request #119 · ChainAgnostic/CAIPs · GitHub
- Add blockNumberTag by TimDaub · Pull Request #25 · ChainAgnostic/caip-js · GitHub
Would be cool if this EIP also included it such that we can link to any historical chain state.