Just a quick update - as mentioned I couldn't find any documentation for the serial commands on the (PAL) LD-V6100 - which seems to be because it's from the same group as the 'LD-V6000A' series NTSC industrials - that is, the LD-V6000A, LD-V6010A and LD-V6200A, which superseded the original LD-V6000, LD-V6010 and LD-V6200.

There is a manual for serial control of the non-A series here on lddb (TP109 Version 2.0), but there is a later version of that manual (TP109/A Version 4.1) which had supplemental pages covering the -A series - the combined volume was at least 156 pages, compared to the 65 pages of Version 2.0.

I know this because one was sold a long time ago on eBay - but all I have are a few tantalising images from WorthPoint! (I contacted the seller but he had no record of who'd bought it).