Personally I thought Bob's explanation on this was quite clear. He stated, in his opinion, the barrels were received in batches & SN'd when received. The frames were then numbered to the barrels when fit up. This meant to me the frames were not numbered when made which Bob explained was why all numbers are not consecutive by build date, but were numbered to the barrels as the frames were fit up to them. This makes more sense to me than any explanation I have heard as to the "Out of Sequence"numbers so common on Lefevers. Thanks Bob for the great research you have done on these guns.
For whatever it's worth I have a reprint of a Lefever catalog with price list dated Jan 1 1889. At the bottom of price list is the statement;
"Barrels imported by us are selected with greatest care, are tested and proved by makers, and bear Government proof marks". I do not have a Lefever with visible proof marks including my side pivot rod cocker from this era, but I know a number of them do exist. Perhaps most of these are on guns numbered close to this time frame.
This catalog shows a cocking rod gun with side pivot top lever. It also mentions the 3 position safety & the top lever being held over by a latch. I will have to look for certain, maybe tomorrow, but am quite certain my side pivot rod cocker has only a 2 position safety & as I recall the lever goes back to center as the gun is closed, being cammed open by the rib extension on closing. Grades listed are Optimus through F & will be built in 10, 12, 14, 16 or 20 at same cost or in 8 gauge for $10.00 additional. List prices were from $400.00 to $80.00. Prices were given for Double Express Rifles only in F grade @ $150.00 or Shot & Rifle combined @ $125.00. These prices included loading tools & bullet mold. Prices for higher grades were stated to advance in price same as double shotguns.
Prices for extra barrels were, depending on grade, from $40.00 to $170.00 on new guns or from $45.00 to $180.00 "to old guns of Our manufacture". It would thus appear at least at this point it did not cost much more to have another set of barrels fitted to an existing Lefever, than to have them fitted when originally built, thus explaining why many may well have considered having an extra set fitted at a later date. Also to be considered is a standard gun could be bought at a discount, rather than ordered direct with a saving which sometimes may have amounted to near half the price of the extra set of barres. It could then have been subsequently sent to the factory for the extra set at regular price which was only $5.00 to $10.00 more dollars according to grade then if ordered with gun from the factory at regular price, thus still a considerable saving by going this route.