How rare is this option?

[Camaro68396]

Hello fellow forumers! Recently, my family has acquired a 1971 Chevy C-20 with the Custom Camper option. I'm wondering if this is a rare option because we can't find anything about any Custom Camper 20 option anywhere. Even in the Chevy truck restoration catalogue we can't find any badging or parts referring to a Custom Camper option. What do we have here, a rare truck or something that is common.