Inner Case Definition
An inner case of cards is simply an interior case within the larger “master” case. Meaning, a master case of cards might come with 24 boxes, but are broken up into two inner cases for packaging purposes. This depends on how many cards and boxes a case contains.
Master Case Definition
Thus, as you can see from this description, a master case is the whole entire case, while the inner cases “mini” or smaller cases within the master case.
Mostly used in “breaking,” a break described as an inner case break is simply to note that the break will not be for the entire master case, but for one inner case.
Take a look at this example from Blowoutcards.com—it’s a 2021 Topps Triple Thread case listing.
As you can see near the top, the configuration is described as “18 boxes per case” but then underneath, that “each 18-box master case contains two 9-box inner cases.”
Read More: What is a Case Hit?
Without this context, it’s easy for one to think that that are inner cases and “outer cases” which from the above, we now know to not be correct. Instead, the “inner” simply means “inside.” Alternative terms that might make more sense could include “interior cases” or maybe “mini cases?” Either way, “inner case” is what is accepted in the hobby.