I question the accuracy of this.
1.8 tons is a big freaking bomb, it is unlikely it could have fit in an unmodified bomb bay.
I suspect there was a mistake in converting between metric and english since we also never used 275 pounders, they were 250 pounds.
My initial thinking after reading this was that it could be reporting yield in tons (equal to 1.8 tons of TNT), but then I reread and the US bomb is in pounds. I doubt they would report one in yield and another in weight.

Quick look around though shows several sources of 2000 lbs bombs; so, it's possible. Conversion confusion wouldn't surprise me either. I think either way we can all agree that it's a freaking huge bomb.
Be an interesting fishing trip if you snagged one and yanked real hard... 
During my search, I found several articles discussing unexploded bombs from WWII still being found in Europe, esp Germany.