Heathkit Post Marker Generators any good?

[Kevin Kuehn]

There seems to have been several models of these over the years that all have about the same controls. Apparently the markers are crystal derived. Do they actually contain a built in sweep generator, or are they an add on post marker generator to be used in conjunction with another sweeper? Anyone have experience using one, good-bad?

http://www.ebay.com/itm/Heathkit-ig-...99567610390714