To build an Inventory Item that has multiple rate cards that count from the same availability bucket, you’ll want to make sure the two rate cards have the same Division, Category Name, Product Name, Name, Unit, Availability, and Inventory Assignment.
The Inventory Assignment will have to be set to ‘Individual.’
Then you will set the Rate Card Assignment for one rate card to ‘Individual’ (for the asset that can be selected on a per event basis) and one rate card to ‘Seasonal’ (for the asset that will be only sold seasonally).
From there, you can differentiate the asset using the Unit of Sale Description (i.e. ‘1 rotational sign/half-inning/game’ and ‘1 rotational sign/half-inning/season’)