Pretty clearly a 6.

It could just as easily be a 5 considering the "bulb" isn't connected

It's definitely a 5. I would expect that they'd use the same tool to cast the '9' as they would the '6' (just turned 180 degrees), and the character in question pretty clearly has a different angle connecting the "bulb" to the "feather" than the '9' in the year.

Plus it looks like the "5" in the "25" below it.

i agree. look at how similar the other 5 is below it. that's the style they used for 5 it seems. I am not an expert but it's convincing enough to me.