I agree.  The fact he was the only one carrying the Explorer MMIV has always indicated it was a private purchase (like the Gerbers were in real life).
The Scalemead survival knife (more readily available in the Explorer Nigh Raider branding) however, was carried by six different marines. 
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	 With so many having one, it is safe to assume that the smaller boot knife was the "standard issue" knife.
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