So, after a week, I have received a response from Turler. VI/48 is not a service marking. It's the date of purchase. Here is an excerpt from the message that I have received:
Thank you for your request. Unfortunatly we don't have any written records.
But in the early time some watchmakers in our company sign the lug with
purchase date (Roman numerals for month and arabic numerals for year).
Therefore, my Turler-signed Roamer has been purchased in June 1948.
If any of you guys have a Turler-signed piece from the 1940s, and find such a marking under a lug, now you know what it means.
Looks like they needed to take their time to respond. I have removed the content of my last post in the previous thread regarding the marking I discovered on the aforementioned watch- the post pretty much expressed my discontent, but once I received a message from them today, I couldn't be annoyed any longer, could I?