最近想去加拿大。有绿卡，加拿大使馆网站如下
For permanent residents, acceptable documents to prove this status would include:
Valid Green Card
Valid I-551 endorsement in their passport
It is also advisable to bring a valid picture ID, such as a Driver's Licence.
请问什么是Valid I-551 endorsement in their passport？是不是在绿卡批准后但还没有收到绿卡之前盖在护照上的STAMP 证明绿卡已批准但还没有收到？如果这样，我几经有绿卡，我还需要出示Valid I-551 endorsement吗？因为我已经换了新护照，STAMP在旧护照上。
请问有经验的朋友我应该怎么办？
多谢！