Constant SEALED_BLOB_HEADER_LEN 

pub const SEALED_BLOB_HEADER_LEN: usize = _; // 14usize

[version: 1][nonce policy: 1][chunk_size: 4 LE][plaintext_len: 8 LE] — the fixed part of the header every sealed payload carries ahead of its first chunk. A payload under NoncePolicy::RandomStored follows it with the 24-byte base nonce; SealedBlobHeader::prefix_len is the whole of it either way.