Assuming that orange eau de vie was unsweetened back in 1895, using 40% Cointreau is quite a bit sweeter. I steep orange zests in Wray & Nephew overproof white rum for drinks that need more orange but not more sugar, so I replaced 1/3 oz of the Cointreau with my homemade orange eau de vie. This was wonderful, plenty sweet, taming the rye in a manner one doesn't usually encounter.