I don't really have “extensive experience in pastry making.” I originally learned the basics when I went to Dunwoodie Baking school in 1956/57 and then worked in my mom’s bakery. I did none while I was in the Army.
I took it up again when I married and we entertained my husband’s business people quite a bit.
That was when I attended Chef Gregory’s French cooking and baking classes.
After my divorce, I decided to try some personal chef work - which I got into quite by accident, helping one of our patients when her caterer quit abruptly.
This is also when I met Henri, a patient who sort of adopted me, treating me like a daughter.
I just did a lot of watching when I would visit Henri - he would put me in a chef's coat and one of those little round white caps on my head and I would hang around and he and I would talk while he worked. Occasionally I got to separate eggs or retrieve something from the walk in or other minor tasks. No one ever questioned me being there because he was the boss of his space. The executive chef thought I was cute and would wink at me but never asked what I was doing there.
Meanwhile, after this discussion began to expand, I got in touch with a friend who is a Brit but has lived in France for many years, has a lot of friends in the business. (she used to be a food writer and asks that I not use her name) She says that a few bakers in France use them, most do not and she has seen different kinds, developed for bakers who thought there might be a better way to achieve the preferred effect. Usually they are just displayed as curiosities, like the carved pins for decorating cookies or other pastry.
She described the ones she remembers.
Most have ridges or grooves end to end, some are large ridges, some are small. Some have grooves or ridges straight around the pin. Some have ridges that zig-zag around the pin. She says she has seen pins with what looks like "hobnails" on them but never in use and doesn't know if they were intended for use as a tutove because some are identify as “lefse” pins.
I sent her a copy of your original post and she says that if your friend is as competent and "starry" as you say, he or she will be impressed just by the fact that you have made the effort to perfect the pastry and even more so for purchasing a tool to make the process better.
She says that the bakery in her village is owned and operated by a woman in late middle age who uses one of the old fashioned tall wine bottles to produce "fantastic" pasty that is the true mille-feuille and not the "ersatz" commercial stuff that is sneaking into many of the commercial establishments nowadays. She works by a window where people on the street can watch and there are often tourists standing and watching her work. This of course, draws people into the shop where her daughters are happy to take their money.
My friend says she has in the past asked about the use of the bottle and the woman told her something like it was to hand. Doesn't quite translate. Her wooden pin fell on the stone floor and a chunk split off. Middle of the night, no way to replace it but she had this big wine bottle so cleaned it and use it and it worked so well she kept using it.