Actually, the row outside of pebbles as well as the internal row are simple pebbles now, if you observes well this photo of restoration(catering) of the panther of Saumur, you can see that the row "power plant" is double
operation "goodwood"
And if you observes even better my photo, besides the markings "continental", the diameter, the nuts, identical hubs, you will report you that the farmer who in tinkered that inverted pebbles finally, before posting these photos here, I showed them has various specialists, as well as has a museum which authenticated well these pebbles as resulting(coming) from a panther