My sister was given a fly rod (vintage) with no fly line weight on the blank. This has raised a question to me of how could the proper fly line be matched to a fly rod blank without any other information than the rod in hand. Anyone have any suggestions?

Are you sure there are no letters on the rod anywhere? You probably already know this and the rod is probably really blank, but older rods were weighted with a letter system instead of the numbers we use now.

Otherwise I can think of two options:
-Compare its profile to a known weight rod of similar vintage.
-Trial and error with several different lines.

There are numbers on it, however they are very difficult to read and they do not match the letter system you are referencing (unfortunately, as that would mean a far more sophisticated and valuable heirloom). It is a japanese fiberglass rod built probably in the late 60s or 70s. I was going to suggest to her a 7 wt line as a beginning as most budget fiberglass rods at that time were not aimed at the 5 wt or less class. The guides are in excellent condition and other than the label being oddly disfigured, the rod appears to be in like new condition (a little rust on the guides). The cork looks unused.

Truth be told, I have often wondered to myself, "self, how does a manufacturer deem this rod a fast 5 weight rather than a slow 7 wt". I suspect a lot of the decision is in the marketing, but still, how could a person decide on the weight of a line given a rod with no information other than the rod itself. Incidently, I suspect the rod is manufactured by Nagoya (sp?).

Picking the best line for a rod is pretty much a subjective decision. Try the rod with several different size lines and then pick the size that "feels" best to the person that will be casting it. For some rods it is obvious which line size works best, but it can be less obvious with other rods.

Most manufacturers use a similar process to rate the line size for rods. They have experienced casters cast the rods and make recommendations on the best line for that blank. For TFO, that caster is Lefty Kreh.

Allow me to interject this website
http://www.common-cents.info/

That's interesting, we did an experiment of Dr. Hoffman's today from a website,
[url=http://www.flycastingforum.net/calib5.htm][/url] http://www.flycastingforum.net/calib5.htm and followed one of Dr. Hoffman's experiments. It indicated roughly a 9 wt rod. Given the age of the rod, that sounds about right as many of the very old fiberglass rods at the cheaper end of the spectrum were in the 8 to 9 wt range. At least she has something to begin making a comparison to.

Zedd is Dead, please go and add to your profile your own hometown. Chance's will go up that there will be offers to meet up and try lines.

Catching a fish may be accidental, but it can happen.

I like to match a red line to a blue rod

Dear StePraDal and Bass Bug,
?
Hugs and Kisses,
Zedd is (not) dead