Splits in F2 shutter curtains
The F2 can be used even when all the light seals (foams) are missing. The only source of light leak on the F2 is the shutter curtains.

Although shutter curtains in the Nikon F2 are made of very tough titanium foils, they do have a limited life. At the end of their life, the shutter curtains split or tear at the weaker points - usually where the end of the foil touches the curtain. The split is usually quite narrow and small, so it can be hard to see. However, the split causes a light leak to the film, and this produces a marked halo or streak effect.

It is possible to replace bad shutter curtains, but parts and labour costs are high. Hence it is now cheaper to buy another used body with good shutter curtains, or reuse the external parts on a lower grade donor body with good shutter curtains.
A small split in the first shutter curtain, viewed from the back.
(Back lit to highlight the split.)
A small split in the first shutter curtain, viewed from the front, with the front assembly removed.
(Back lit to highlight the split.)