That would be a US spec car as the 4.5 was only sold in North America in order to meet new emissions regulations. The 3.5 was a sweeter engine as it ran a higher compression vs. the US 4.5. The 4.5 used a 3 speed 722.0.
Being a US car, it's a good chance that it's rust free.
I had a 280SEL 4.5 which went to Spain in 2009. That was a great car. I sold it when I got my 6.3.