You can't be certain unless the cover came with provenance documents from an astronaut or has an astronaut's annotation on the back. In short: Prior to the mission they signed stacks of covers. Some were given away to space workers and other astronauts prior to the flight. Those are NOT insurance covers. Some were set aside and held by the family as "insurance." Those are insurance covers. So you can't tell just from the type of cover if it was insurance or not.

@ZarelliSpaceAuthentication Thank you for the clarification. The three that I obtained was from the collection of Houston's Post Master at the time. His name was Grenville Elder. One of the covers is addressed to him, the 2 others are not addressed. I will look on the back of the cover to see if there are any annotations. A question for my knowledge. If they are or not insurance covers , what realistic market value would you place on them? Thank you.

X-15 multi-signed are great. I have seen a number of them over the years. However, they also occasionally used rubber stamps on these. Use my email opinion service for a review: zarellispaceauthentication.com/services Select "Apollo 11 Crew" for $20.