Caseback number 12042 (that's a match).
Movement number 04030863.
The movement serial is the early type printed into a medallion (not engraved onto the movement, as was done later).
There are two service dates written inside the caseback - VD - 11/03 and MH - 09/98
My 5100 movement number dates would indicate that this is from the late 80s, a slight possibility of early 90s. It is the earliest serial number I have, only a couple of thousand away from the Lederer chronograph I used to own which was a clone of the Heuer 510.501, produced 1980 onwards. To my reckoning, the 510 series clones made for Lederer and Tourneau will have been made in the last days of Heuer, and not during the tenure of Tag, so the end date for production would be 1987.
The movement serial being such a close match would date the Lorenz from that period, but as ever, I am totally open to further information.
If it's Lemania-powered, I'm interested. Tool Chrono - interested. Dive Chrono - interested. Interesting - interested