Full ivory and full imitation ivory offer the best insight into a maker's product. Here are a few examples of full ivory Hardie instruments.
The Hardie above is a 1950's version whereas the Hardie to the left was made in the early 1960's. The style of the chanter helps us here. You can see that in the 1950's the chanter went straight into the sole. Afterwards a bull-nose was introduced. In the middle to late 1960's Hardie produced a chanter with no sole. Muirhead and Sons Pipe Band played those chanters to five consecutive World Pipe Band Championships with those chanters. They were denied a sixth Championship under questionable circumstances.
The Hardie bagpipe below was made just prior to the ivory ban in 1976.
In the A/B picture you can see how the cut-in atop the projecting mount is much wider than the facing ferrule.
R.G. Hardie