There is ON at the end of the following sentence.
Remaining aloof was no longer safe under the restored democracy of 403 on.
403 is the year.
I think without it the sentence makes sense enough. I know there is no usual sentence that ends with a preposition and there is no object of it. If I understand it as an adverb I can't find any verb that matches it.
Does it have any special meaning? If so what does it?