DULY HAND SIGNED是手签还是盖手签章 STAMPED是说盖长条章吗

coomercial invoice duly hand signed and stamped by them stating that: goods are of chinese origin. 信用证中如上， duly hand signed 是手签还是盖手签章， 后边stamped by是说要盖长条章吗？ 先谢谢各位大侠指教！