I don't know the logistics of creating a vintage size chart spanning all the eras. Women wore corsets and girdles, some even until the 70's which creates a TOTALLY different bust/waist/hip proportion than what was the norm in the 1980's (except if you have a naturally hourglass shape and then wearing modern clothes is hell!)
Even vintage bras gave the bust a much higher bustline than what 70's and 80's bras did (women who wore bullet bras in the 50's must think that the women of today have rather saggy ones!), which is why the darts on vintage dresses don't match up with your bust when you try it on with a modern bra and then your boobs end up at the waistline.
I think your best bet would be to give concise and clear measurements. I give shoulder, bust, underbust on fitted things (as corsets and longline bullet bras pull in your rib cage), waist, hip, sleeve length (including cuff measurement if it's tight fitting), garment length and even torso length (from shoulder to waistline) so if you are short or long waisted, you can see if the proportions will be appropriate for you or not.
Sometimes you can give a general size if you try on an item. I'm a US size 10/12 (UK 12/14) and 5'9" and can generally see what size range an item will be judging by the fit it is on me so I will give an approximate size as well.
LOL, hope this gives you some idea of what your in for :D
Lei
