Anyone collecting OPC in the last few years knows UD makes a blank back version of the base cards and makes them rather rare to pull, but what I didn't really know was that blank backs had been around long before that. Here is an example.
Front side, seems normal enough, condition is excellent-ish
Back side.....blank as my mind some days
If you look on eBay, you will see many blank back cards from the 50's-present day and those seem much more plentiful that I could have ever imagined. Personally, I never pulled one of these from back in the day or in present-day products.
The questions I have are:
Are blank backs from the 90's and previous rare?
Were they made on purpose or are they an accident?
Are they valuable in any way?