Thanks, all! I’ve known that the packaged weight is the head content only. @Catt helped me understand the logic by the different types of blades and things used to build the spinnerbait. I hadn’t considered that and it makes a lot of sense. You’re right about the Senkos, @Munkin. Normally they are pretty close to 3/8oz when you put them on the scale, but I have seen some more and some less.

It is good to see that folks other than me have solved the "What does this weigh?" issue.  $20 to $30,  a trip to Walmart and all of a sudden you're the proud owner of a postal scale.  If you buy a decent box to put it in and remember to take the battery out when you store it, they last a long time. I got mine in 2008?  2009?   Anyway, now it is where it is supposed to be, in a box in the fishing shed, waiting to get called on to weigh something.