I'll have another go at this.
The units property reflects the insunits value of the drawing.
A standard inches dwg will have
INSUNITS=1 DEFSOURCE=1 DEFTARGET=1
A standard mm dwg will have
INSUNITS=4 DEFSOURCE=1 DEFTARGET=1 (Cad blunder, 4,4,4 is better)
To create a truely unitless drawing you need
INSUNITS=0 DEFSOURCE=0 DEFTARGET=0
as a mm dwg with the INSUNITS set to 0 will still have
DEFSOURCE=1 DEFTARGET=1 and so will insert like an inch drawing.
So Humbertogo you may need to change all the unitless dwgs to their correct setting.
Unitless blocks are handy for
? unit circles of 1 unit, confusing people, making refernce blocks.