The P61 is the variant known as the Musketoon. It is the shortest of all the P-H replications, but is just as well-made. Like the original, it has progressive depth rifling that gets shallower from the breech to the muzzle - a real feat of engineering. It was used by Dragoons - infantry who rode to battle, and artillery - who needed a much shorter rifle to manage when on their horses, and anybody who fancied a very handy weapon with some serious clout as a short-range firearm. that 535gr Minié bullet at 1000fps could really make your eyes water.
The P58 is the two-band rifle, sometimes called the Navy rifle. It is the favourite of many shooters because not only is the barrel some 6" shorter than the three-band P53, it is also thicker and therefor stiffer, leading to great accuracy. On board ship the shortness was an asset, as all space was at a premium.
If you have been reading the
dozens of post here recently, you will have read that Parker-Hale ceased production of all their firearms products in the early 1990's - opinions differ as to when this actually happened, but let us say that it was 1992. I'm sure that THE Parker-Hale expert, David Minshall, will pop up and put us right.
By that time, Parker-Hale had produced around 9000 muzzleloading rifles [and a few smooth-bored Musketoons] of all kinds. Sold off were the entire assets of the factory, including another ~5000 PROOFED barrels, to Euroarms in Italy. They were already stamped with 'Parker-Hale Birmingham' and showed Birmingham proof marks under the barrel at 6 o'clock, and a serial number on the left side adjacent on the breech - like this on one of my P-H Whitworth rifles -
Euroarms in Italy continued to make all the patterns of gun for which they had barrels and parts to do so, right up to about serial number 14000 or so, when ALL the barrels had been used up, and they could no longer be sold as Parker-Hale-barrelled firearms. A few Whitworth barrels seem to have ended up at Davide Pedersoli SPa, who made them up and sold them with Parker-Hale and Whitworth clearly stamped on them.* A poster on another forum sent me images of his, and I wrote Pedersoli asking for an explanation and was told about the use of P-H barrels for a time. Needless to say, they were not keen to tell me how many there were, but it's fair to to say that the guns show at IWA in 2016/17 were probably wearing P-H barrels.
So your Navy Arms/ASM rifle has no connection with Parker-Hale of any kind, having been made and proofed and dated [yes?] in Italy in 1982, when P-H were still producing their products. The rifle you see above dates from 1986, BTW, but may not have been made in that year. Only examination of the proof marks can tell us the year it was proofed. This one is even earlier -
and this Musketoon of mine, oddly older than both but with a higher serial number of 1137.
So here are two Whitworth rifles -
I don't have a P58, but I DO have a Canadian Snider Short rifle of the same dimensions, as it shows the five-grooves and thicker dimensions of the 1862-dated P58 from which it was converted - I hope Zonie will forgive me for this one -
and the 3-band Snider converted from a 1862-dated P53 -
The difference in barrel length is clear.
* If I can find that correspondence, and the recipient give me permission, I'll post it here, Okay?