Buckley's Buckler is an enchanted Buckler sold at The Friendly Arm, but only in the Baldur's Gate: Enhanced Edition version. In addition to the normal Buckler properties, it offers +1 to Constitution so long as it is worn.
|“||A rectangle of mammoth hide forms this small shield. No amount of cleansing can dispel the pong of decay from this poorly tanned device, yet somehow the malodorous shield fortifies its wielder.||”|
Characters with a Constitution score of 20 begin naturally regenerating hit points at the rate of +1hp/turn (1 turn = 10 rounds = 1 real time minute, or 10 minutes of in-game time).
If during character creation the player chooses a race of Half-Orc or Dwarf and sets their Constitution to the max of 19, then equipping Buckley's Buckler will give the CHARNAME regeneration as soon as the The Friendly Arm, in Chapter 1.
Other races (except for Elves) will have to wait until they acquire the Manual of Bodily Health. Elves cannot naturally regenerate at all in BG:EE.