No, no one knows.

COURTESY OF BRUCE MILLER:
I took two field guns to the original Ithaca before their closure in the mid 80's. My instructions were to give both guns a muzzle to butt restoration. The gentlemen in the Custom Shop disassembled both guns and immediately identified their individual maker. Apparently each man at Hunter left identifying marks or something of the kind. The men at Ithaca spoke of the men at Hunter as if they were merely out to lunch, not as if most has passed from this world several decades previous. Fact is, they pointed out equipment on the Ithaca floor which had previously served at Hunter. Equipment that had likely seen my guns years before.
In the case of my nickeled gun, it was pointed out to me why the work had to be done at Hunter. Mostly a matter of fit. Nickel plate adds dimension to anything plated. Thus, either very professional masking is involved or certain dimensions must be changed to allow for the procedure. When I suggested "aftermarket" they just laughed and pointed out that the job was obviously factory as dimensions were all perfect. In fact, they knew the firm in Rochester that had done the work for Hunter.
Before the gun left for de-plating I was shown the various components. Each had been masked to maintain vital dimensions previous to having been plated. The lockplates showed no sign of case colors on the inside surfaces. The boys at Ithaca said my gun was not in the least unusual and pointed out that the Great Depression led to many unadvertised options being offered by Hunter as a dollar here or there was most important.
This is a recounting of what I learned and was shown. The men at Ithaca are now long gone as most of them were past retirement age then. Given that Ithaca was in about the same financial shape in the 80's as was Hunter in the 30's, I found their stories credible in that Ithaca would have done the same thing to make a few extra dollars.

As yet, no gun specified as having nickel plating has been identified in the Hunter Arms shipping records. Unfortunately, the order records no longer exist.

HAVE YOU OBTAINED A RESEARCH LETTER BART?
https://lcsca.clubexpress.com/content.aspx?page_id=22&club_id=43784&module_id=245742

There WAS a room in the Hunter Arms factory for nickel plating, but it could have been used only for Hunter Fans. No. 9 at bottom