Cavalry Brigade (Pleasonton)
5th US Cavalry (all 12 coys?), 8th Illinois (all 12 coys?), 1st Massachusetts (8 coys, A-H), 4th Pennsylvania (all 10 coys?), 6th Pennsylvania (7 coys only) and 3rd Indiana Cavalry (all 6 coys?)
(8th Pennsylvania Cavalry arrives 18th after a recce towards Gettysburg, PA)
Thus I can make a stab on the strength on the strength of the cavalry in the centre. At 30 sabres per company there would be about 1,600 sabres in the centre. This being a question a posed over a year ago resolved.