Bad traders

what the others are saying; its been used already with a brake and you can easily use it with a brake.
see some previous discussion on here bout non-machined vs machined:
https://www.lfgss.com/conversations/128720/

another subject but, why not first try fixed with a sensible ratio and maybe double brakes?
you could always go singlespeed afterwards.
ild do that; what cog is on there/what chainring do you have up front?

if the bike is ridable you are very welcome to come by mine and use some tools. otherwise i can thoroughly recommend the guys at keirin cafe (dunno if they opened up again) or goldsprint. at keirin the guy even let me use his tools for freeish and was very nice overall. at goldsprint and also keirin they help you with a lot of stuff at the spot if its not too much bother..
as said, will be back on the 22nd. also have a freewheel if you are not set on my proposal and if its a suitable ratio you can have it for cheapz and i'll help you to swap the cogs.