Here are a few for your comparison study guys. This first is an insert that lives on my 1974 1680. It is the only one of the bunch that I have not acquired in an original factory blister pack with part number. I have often seen this referred to as a mid fat font insert but have no idea what MK number it is. The next three were all purchased in factory sealed boxes of the same part number. (B315-5513-1-A1) These are all gen inserts and you can see that there are 2 examples that have the flat vertical on the back of the 4 and two that come straight to a point. I guess it goes without saying that I prefer the flat top 4. Also I have purchased the same part number at times that has a thin font insert with no serifs! It can be like buying baseball cards. You never know exactly what’s in the package unless the seller gives you a good picture of the box and insert. Hope this helps...