The visible tier of a lock. With days, the tier a term of that length reaches and how far the next one is. With wallet, the tier that wallet currently holds, read from public lock records. Both are optional and independent; with neither, returns the tier table. The tier is derived from the TERM a lock was signed for, measured from its on-chain creation to its unlock, and clears a threshold within one percent of it. It grants nothing: it is never stored and the boost multiplier does not read it. Size is not an input, so the same term reaches the same tier at any balance. Read-only.