Atco lawn edgers, most collectors have at least one, the dating of these is often confusing so here's my understanding.
1923 The first edger of this style introduced by Atco, this had a wooden handle with a cast plate that held the spanner for adjustments.
1934 Similar to above with wooden handle, but now with a detachable grass box or trough to collect the clippings.
1940's Metal tubular handle with shaped alloy casting for the hand grip.
1960's - 70's Metal tubular handle with rubber hand grips.