These are games that should not have 5-screw variants, but do anyway. There are theories about why they exist but there is no solid evidence yet. These games are true anomalies in the NES library. The games by Konami/Ultra that normally should have 5-Screw variants are not listed here. These missing titles are Castlevania, Double Dribble, Goonies II, Gradius, Rush'n Attack, Stinger, Top Gun, and Track & Field.
Edit: Given some new information, it seems that early Konami games can also come in these "Konami 5-Screw Mystery Variants". The on going pattern is they use later labels (such as Oval seal of Qualities) and have no rear label. I've now added all early Konami games as "Possible" and will await proof to begin coming in."
- https://www.videogamesage.com/blogs/entry/19-usa-list-of-nes-hangtabno-ht-5-screw-3-screw-variants-v13/