There is a lot said against brass, mainly from America, because of the very small quantity of lead in the brass alloy. In reality this is miniscule (3%), and the zinc is more likely to leech out than the lead. They still make brass fittings for water using this and nearly all taps are made from brass, and most of your water pipes used leaded solder, so I would be happy to use it.
Just check the base of the weights because they did use solid lead to adjust the weights for accuracy. It's usually only on iron weights (as a hole) but possible they would do this to brass as well.