Landships II

Researching a little of the background on Sigfried Sassoon's Military Cross (MC), a dead-end line of enquiry lead to http://www.fn-browning.com/fn.htm and the correction of misconceptions about the FN Browning automatic pistol in Belgian service (army) which might be interest (Anthony Vanderlinden & Mary Vanderlinden).
The Belgian military only adopted four pistols in the pre-1940 era:

1. The 7.65mm FN Browning 1900 in the year 1900
2. The 7.65mm Colt 1903 during WWI as FN was occupied
3. The 7.65mm 1910 model in the year 1919
... - which are presented as the facts.  The Colt was a Browning design by the way - often described as the "Browning M1903" but Colt had purchased the design.

Where Sassoon came into it was that his "other" pistol, privately purchased in 1916, is assumed to be a M1900 (but .32 ACP/7.65mm not 7.62mm as often stated).  It seems unlikey to me that many spare M1900 would have been available during the war - perhaps it was the similar-looking M1899, the rights to which FN had purchased but which, as the FN Historical Society says,
The FN Browning 1900 was introduced in 1900 after Belgian military trials requested changes to the Model 1899
- so it would seem there was a far greater chance that a private purchase in 1916 might be of the M1899 when there was probably a shortage of M1900s.  But that ended up having nothing to do with the MC story.

For uniform detail - the M1903 typically had a much longer barrel and slide than the M1900 (127 mm Vs 102 mm - 205 mm overall Vs 172 mm though I haven't verified that for the military issues), if so the holsters would look quite different though both would be "authentic". Okay, 32 mm doesn't sound much but those holsters would look quite different, trust me.  Also the rear sight platform of the M1900 is typically shown as beeing much bulkier than the M1903, leading to further differences in the holsters.  Unless Belgian officers carried their pistols in their pockets, as Sassoon did with his M1899 or M1900 - certainly those were quite 'concealable' weapons.  A bit of supposition I'm afraid (that the Belgian miltary models closely conformed to the examples in Jane's).