Don, I dunno if the blade is flat ground, though I kinda doubt it as RMK doesn’t make too many flat ground blades...but, Miles could prolly look at his face-on, from tip to hilt, and see if it is indeed flat, or if there is an ever so slight dip...

Steve, let me help ya out here. Gaddis wrote on page 162 ’13 May 1957, #16 Solingen Blade – James Jones – Marshall, Ill.’ On the next page he wrote of one being sent to Jones in March of 1958, followed by commentary about the fourth Model #16 being ordered in January of 1959. So, take your pick of dates

All, as to catalog introduction; the Diver’s knife was shown in the 12th catalog printing of early (February?) 1959 on page 12, available in stainless steel only – the 14th catalog of late 1960 showed availability of both steel types. See that part in the catalog page you posted about 'Swedish Steel'...that references O1 high-carbon tool-steel. (Doh, Tom beat me to it...lol)

So, carbon steel obviously became an option sometime between those two dates; just when is still up for debate. (although IIRC, it 'was' available in 1959)

The model #16 continued to be offered with a Carbon steel blade until just prior to the release of the 21st catalog in early 1971...so, through 1969 and possibly into 1970. As you already mentioned though; the stainless steel type indicator markings, whether stamped or etched, weren’t used until 1963. Tenite was all but discontinued by early 1965.

So, shootin' from the hip here - at the very least, carbon steel Model #16’s ordered between the latter half of 1960 and the middle of 1963 would, theoretically, be externally identical to their stainless steel brethren.

Hope that helps