Yes! In fact the second one I saw was ALSO stamped patent applied for.
I can imagine a few possible reasons we’ve seen more of this size:
The original invention was in response to a need best served by this size (clearance, for instance).
The manufacturer anticipated a larger market for this size (related to reason one above), so focused on producing more.
Consumers, to try out the product at the lowest investment level, purchased the model offered at the lowest price point. As a sort of corollary, the 7” model could have been manufactured and distributed on prospectis.
Larger models were subjected to greater abuse, so have not survived in proportunate numbers.
In any case, it seems clear to me that they never penetrated the market establishblished by Petersen in a big way. The Asian knockoffs are nonexistent, and you don’t hear anyone say, “hand me those BMCs” as a generic term, but rather “visegrips.”