I've not used that particular company before, but one very similar to it from
AutomotiveTouchup.com. This wasn't for 504, but in general I've found their formula mixes are hit or miss. One car I had was a near perfect match, the other wasn't even close. The other thing I didn't like was the paint was only available as a two stage which it hard to match in appearance to the original single stage paint. If you have a little time to be patient, I would recommend
Tower Paint. I sent them the ashtray from my old Beetle and the paint code and within one week I had a perfectly matched color in a spray can. The best part, they can make it in a single stage lacquer! I was so pleased with the results, I won't get paint from anywhere else.