Those splendid chaps at the Mills equipment company (Meco) often re-utilised a successful design in later patterns that has caused the modern collector a bit of a problem, the 1919 pattern Naval ammunition pouch was repeated in blue fabric for the RAF 1925 pattern as an ammo pouch and then again for the RAF blue 1937 pattern as a sten gun loading tool pouch, both the Naval 1919 and the RAF 1925 pouches were discontinued in 1940 being only ever made by Meco, the identical looking tool pouch was made by lots of companies from 1942 onwards, the sten gun loading tool was a sprung plunger that slid over the end of a metal magazine so you could pop bullets back in to fill it up, to do this in the field was impractical why not carry spare magazines and refill them back at base ? as a result these loading tools were ditched faster than a gas mask leaving vast unused stocks of the blue tool pouches which are still around today, 1919 collectors do not want them as they are blue and 1925 collectors shun the too-late dates and the 1937 blue ammunition pouch was much smaller so even today these tool loading pouches are unwanted making them both cheap and available.
Back in 2011 there were two 1919 ammo pouches in my collection and I was seeking a third so when one appeared on an on-line auction site I bid £120 and won, although quite blotchy the item had no markings apart from a large N and was put away in a drawer, when I was ready to use it I followed my usual routine of washing prior to polishing the brass, I soaked it in warm water with a single drop of washing up liquid and began gently cleaning with a soft nail brush and I was astounded to see the water turn first yellow then purple as the large N floated away, when dry a close examination revealed that there was RAF blue stitching and large areas of white fabric inside and a shaved area where a date stamp had been removed, the chemical smell present was identified as a well known bathroom cleaner, 15 further pouches followed on-line from the same dealer yet in 12 years of collecting this pattern I had previously only ever seen 4 examples of the 1919 ammo pouch which remains as rare as the cutlass frog and water bottle carrier.
When sprayed by a certain bathroom cleaner the unwanted wartime dated tool loading pouch turns entirely white yet all of the original stamping stays intact to which an N and a depot number can be added using modern ink stamping kits, colour this brown and you have khaki pouch, shame about the makers and dates.
In 2012 the white 1919 Naval ammo pouch with its too-late dates was invented without a matching belt, the fact that it was completely unknown to Naval archives was overlooked along with its RAF blue stitches, the second example sold on-line completely lacked a depot number.
Your 1919 Naval ammo pouch should be khaki (or blancoed white) and be made by Mills so will have MECo stamped inside and have a large N and a depot number if made between 1919 and 1939, however the last year of manufacture was 1940 so examples with this date have the depot number and N replaced by two small numbers over a U which is the utility stamp meaning that it was funded by the Ministry of Supply.
The MECO company stamp changed to MECo from 1923 onwards and the large Naval applied N altered becoming smaller from 1937.
All 1919 pattern Royal Naval webbing was made without exception by the Mills equipment company who stamped every single item with their MECO logo and the year that it was made, all production of this pattern ended in 1940 along with the 1925 RAF pattern to concentrate all production on the Army 1937 pattern which was adopted as the new tri-service webbing pattern, prior to World War Two when each piece of Naval webbing arrived at a dockyard depot it was inspected and given an N ownership mark and an inspecting depot number before being sent on to issuing stores on ships or stone frigates (bases) but all of this changed on the outbreak of war when the new Ministry of Supply took over all equipment purchasing to Admiralty demand, all outstanding 1919 orders were completed to clear the way for the new 1937 pattern making the 1940 dated 1919 items by far the most numerous examples made.
Any changes to 1919 webbing were meticulously recorded and published by the Admiralty and I have never seen an Admiralty directive that moves the brass closure popper on the holster so if your popper is not in the right place it is most definitely not Naval, almost identical versions of both the early and late model 1919 holsters were made by Mills for private purchase with the popper moved nearer the barrel tube as shown by the orange dots on the picture below, these private purchase examples are of course much rarer than the Naval ones, a similar styled holster was made in 1941 with a top hook never seen on Naval holsters and this 1937 model was then shrunk for the smaller .38 caliber revolvers and reproduced in Australia in their characteristic stripey canvas.