The four staples on the right breatsplate (acc. no. 29.150.99) are for the attachment of a lance rest.
Marking: Marked six times in pyramidical form, on the inner side of the right breastplate: AN (or possibly AM, indicating a possible association with Antonio Missaglia of Milan, working between 1451 and 1490).
Blair, Claude. "The Emperor Maximilian's Gift armour to King Henry VIII and the Silvered and Engraved Armour at the Tower of London." Archaeologia, or, Miscellaneous Tracts Relating to Antiquity 99 (1965).