Icon IC 743 piston weight incorrect

I have 469 grams for a stock Magnum piston. If the OP's numbers are correct, then he would be over 80 grams heavy compared to the stock bobweight. It ID odd that a domed piston would be lighter than the equivalent flat top piston in the same series and size. (IC741)

OP what weight did you get for a single Magnum con rod with cap and fasteners, no bearing shell? My data shows 744 grams + or -.

You can check your scale for incremental accuracy if you an accurate cc measuring device like a burrette used for checking head chamber volumes. Put a glass measuring cup on a see the weight then start adding water with the burrette, each cc is 1 gram. Add 100 cc's and see if the scale weight goes up 100 grams.

BTW, I have the same scale as one of my 2 and they are accurate if used right; I checked them against the local machine shop scale. But this still could be a scale problem. These type of inexpensive scales need to be PERFECTLY level or they can read off. If tilted, any sideways loading of the scale's platen will throw off the cheap strain gauges used in them.