Alvin Keech started making banjoleles in the late teens and finished up, I believe, in the early 30's, so it's older than 40's. He made several different models, and if you can, you should post a photo.
Over the last six months, I've tracked Keech banjoleles on eBay and six have moved. They're not common, and they go for a LOT more in the UK than they do elsewhere in the world.
In the UK, the six-tensioner model with the floating head assembly (basically the junior model) has gone for $411 US for a fully restored and refinished model, $231 US for one in excellent original condition, $106 US in VG condition with quite a bit of wear, and $416 US for one in mint condition. A different model went for $159 US - a longscale listed in very good condition.
The same six-tensioner model in what I would call VG+/excellent condition - sold in the US for $90 in December. In the US, they just don't have the name association or cache that they have in the UK.
So is it worth $170? Depends on the model, the condition and what you want to do with it. If you plan to play George Formby style, the Keech banjolele (which he didn't play but it is ironically associated with him) is not an easy instrument to play in that way as the action tends to be somewhat high, though it can be adjusted. Otherwise, its a fine instrument for other playing styles.