Before that discussion, I had been aware that there have been heated discussions among reenactors and historical costumers about whether the Vikings used lucets or not, but I didn't really know what support existed for the hypothesis that they used such devices. It turns out that the most solid piece of evidence for the use of lucets in the Viking era comes from a grave find at Barshalder, in Sweden, which was the subject of an article by Kerstin Pettersson. Here's the full citation of her article, for the curious:
Kerstin Pettersson, "En gotländsk kvinnas dräkt. Kring ett textilfynd från vikingatiden," Tor 12, 1967-1968. Societas Archaeologica Upsaliensis, Uppsala, pp. 174 - 200.
The Barshalder cords have a square cross-section, like the cord made by lucets, according to Sandy Sempel of Frojel Gotlandica, who has had an opportunity to see them in person. Like lucet cord and unlike cords made by fingerlooping, the Barshalder cords appear to be made from one continuous length of string. It seems likely that, if cord with the physical properties of lucet cord (shape, made from a continuous piece of yarn, etc.) is found in a Viking era grave, that the Vikings had a device that could make such a cord.
There are an astounding variety of different objects from Viking period digs that have been labeled as lucets. They range from elegant, highly carved and decorated two-pronged objects, to elegantly shaped but rather plain tubes with prongs, to pointed and crudely shaped pieces of bone. I am far from convinced that all of these items were used for the making of cords of any kind. Any two-pronged object can be used in the same manner as a lucet to make cord; I've even seen a picture of an upside-down chair being used to twine a rope. It's even possible, I'm told, to use two outstretched fingers for the purpose in the same manner as a lucet. If two prongs are all one needs to have a lucet, then all of the above objects can certainly be used as lucets. But that fact alone does not prove that Vikings actually used all, or any, of those objects that way.
One might argue that Vikings typically ornamented their textile tools, so the plain pieces of double-pointed bone were unlikely to be cord-making devices. On the other hand: 1) some needlecases, for example, are unornamented; 2) some of the deeply carved "lucet" examples would be difficult to use for the purpose, because the string would be likely to snag on the carving; and 3) plenty of reenactors have successfully made cord with bone or wood models of just about all of these devices--even the "rough" or "pointy" ones--making it difficult to exclude any of the proposed "lucet" finds on the grounds of impracticality.
This type of device will probably be familiar to those of my female readers (at least) who may have received one as a "craft" type of gift in childhood. Even now, this type of device is commonly made in bright primary colors and/or fashioned to look like an animal or doll figure. They are often marketed as toys for children. The term that most reliably tracks down such devices on Google is "knitting nancy". They are also called "spool knitters". The British sometimes call them "corkers". I've seen them called Bizzy Lizzies, and models made by various companies probably have different brand names. These "knitters" typically have varying even numbers of pegs, mostly either 4 or 6, but I owned one when I was a child that had at least 18 pegs and could be used to make a fairly wide knitted tube all by itself. And as the pictures I've located of Viking finds suggest, at least some of them look like two-peg spool knitters.
While I was looking for examples of spool knitters, I ran across this blog entry in which the blogger, inspired by an old book called "Spool Knitting" by Mary McCormack, experiments with making cord using a device she calls a "Cordelia cordmaker" that is not shaped like a lucet or a knitting nancy but, like them, has two pegs. She describes using the cordmaker using the same type of technique followed by McCormick with her two-peg knitting nancies:
McCormack does all her spool knitting on 2 peg spool knitters using the figure ‘8′ wrap. She doesn’t start with a slip knot, just by taking the yarn around the right hand peg. She uses a dowel with a center hole that she drops the yarn down, but since I am using a Cordelia cordmaker that doesn’t have a hole, I just hold the tail in front of the cordmaker. ...
So, you take the yarn around the right hand peg, between the pegs, and around the left hand peg, then back between the pegs……and around the right hand peg again. Then, you lift the lower wrap of yarn over the upper wrap…. of course, I had to take the picture, so I left the loop lifter dangling in space, but you’re not going to do that…
McCormack has the reader take the yarn around each peg, always following a figure ‘8′, and lifting the lower loop over the upper loop.
This creates a cord that is actually closer to being square than round (emphasis mine).
So here's the question. Do a two-pronged spool knitter and a lucet make structually identical cord? I think so, but I'd need to obtain a lucet and a suitable spool knitter, learn how to use a lucet, relearn how to use a spool knitter, and make a test cord with each device to confirm that theory. If both cords are identical, that likely means that a lucet is functionally equivalent to a two-peg spool knitter.
Unfortunately, my proposed experiment still won't prove which, if any, of the two-pronged bones from Jorvik, the ornately carved two-pronged bone devices from Scandinavia, or any other potential "lucets" from digs were actually used for cord-making. But it may suggest that the "spool knitter" is an older device than most people assume it is.
EDIT: The gentleman who wrote this site apparently believes that I have the causation backwards in my last remark. He states that the various versions of spool knitters "all owe their existence to the medieval lucet." It may well be the case that the lucet came first, and the spool knitter is a later improvement upon it. All the same, I wish he had reported the source of the information upon which he based that statement.
SECOND EDIT: Apparently the name "knitter" for the spool knitters is not misplaced. It is possible to "knit" a similar cord just using ordinary knitting needles. This blogger writes about doing so; she calls the end product "I-cord." This page describes how to do the technique.