The M1917 rifles, or M/53(17) as they are officialy named by the Danishmilitary, that are being used by the Sirius Patrol in Greenland does still have their original rear sights. The Sirius Patrol is a Danish military unit and uses the rifles in original condition as issued and they are as far as I know not modified in any way.
The M1917 rifles with cut-off rear sights are surplus rifles that were modified and sold to the local civilian hunters in Greenland via the Kgl. Grønlandske Handel which roughly translates into the Royal Greenland Trading company. The reason for the modification was because the hunters didn’t want the peep sight as it was easily blocked by snow and ice. The modification was performed by Kgl. Grønlandske Handel who used a subcontractor to do the actual work. The Danish militay has not used rifles where the rear sight has been cut off.