. should actual product marketability and raw material fitness for use be affected by conditions that are different from management estimates , further adjustments to inventory allowances may be required . snap-on adopted the 201clast-in , first-out 201d ( 201clifo 201d ) inventory valuation method in 1973 for its u.s . locations . snap-on 2019s u.s . inventories accounted for on a lifo basis consist of purchased product and inventory manufactured at the company 2019s heritage u.s