I was asked to restore one of these about six years ago, to match up with a WW1 Holt Tractor. I was told that it had been one of a pair used on the firing range at Foulness, and the other one had been restored and had gone to New Zealand. The one I started on was missing most of the 'Trail' and had no barrel. It just had the WW2 wheel hubs and spokes with no outer rims, which were fixed into a frame presumably to steady it when firing. I went down to Woolwich with some friends to see 'Spikes gun', The Curator was very obliging, and allowed us access to the library where we gained very useful