Value of supply through agent: open market value or ninety percent of recipient's comparable sale price governs valuation. Rule 29 values goods supplied through an agent by reference to the open market value or, at the supplier's option, at ninety percent of the price at which the recipient supplies like goods to unrelated customers. Where valuation is not determinable under that provision, specified fallback valuation rules apply in sequence. Certain exclusive commercial relationships are treated as related persons, but a sole agent, sole distributor or sole concessionaire is not treated as an agent for this valuation purpose.