It's become a truism that American troops tended to call any German artillery an 88. I don't think that holds water at all, and may be a fiction created by correspondents or perhaps green troops in their first fighting encounters. Repeat anything often enough and it becomes "truth" and this particualr wisdowm has been repeated so often it has become cemented in place. In my reading down at the nitty-gritty level (mostly based on 30th ID accounts), it's rather obvious that the GIs in fighting divisions certainly knew the difference between direct fire weapons like the 88, and long range artillery like the 10.5cm and 15cm guns. What they did do is tend to call most direct fire weapons (whether mounted or towed) an 88 even though the great majority were in fact 75's, and even that may have been because they hoped counter-battery fire would prioritize their particular fire mission if the target was an "88." In any case, I doubt anyone could reliably tell the difference between a 75 and 88 when it's sniping at you from a kilometer away. This becomes particularly evident in accounts from Mortain, in August 44. In the early morning hours of 7 August nearly the entire line began taking sporadic direct fire from across a shallow valley. Reports going back to battalion and regimental headquarters were very clear that the flash and report of the guns was followed by the hit of the shells a moment later and often this fire is reported as an "88" which may have just been shorthand for direct fire. In the darkness it was unknown whether these were panzers or towed guns, but since outposts and fleeing French civilians coming through the lines had reported tank noises, the fire was generally reported as coming from tanks (and likely most of it was in that opening contact). Later in the day as German probes more clearly revealed the American positions, the Americans began taking indirect shells from heavier German guns much further away, and this too is reported correctly as "heavy" artillery from unknown locations. As the light came up, the observer on Hill 314 (Lt. Weiss) began directing a complete symphony of fire from an enormous amount of batteries (as they came online), to a variety of German targets, both fixed positions, attacking units and more distant fixed artillery revealed by flash. Weiss was certainly not confused about direct fire guns vs traditional artillery, though he too referred to the direct fire he took among the rocks on the crest of the hill as "88' fire. It may have even been fire from an 88, though it's far more likely it was a 75 (tank, towed, mounted, take your pick). To my annoyance (as an amateur historian) the 30th moved on from Mortain immediately following the battle, and as is usually the case, little of the post-mortem of the guns and vehicles found at the site is associated with the division, that info being the within the purview of various clean-up and ordnance units, and thus lost. There are a lot of photos of the panzers (mostly panthers and Mark IVs) found right at the line are available, but there is nothing on the various (less photogenic) guns destroyed further back via long range direct or indirect fire. Yet, in the following weeks as this division and others followed up the retreating German army into Belgium, Holland and Germany itself, a number of lset-piece battles occurred in little towns and crossroads. The Germans would leave a gun and an unlucky company or platoon to slow up the advancing American forces. Most commonly, the "88" was a 75mm PAK 40 (or similar variant), though a surprising number of these encounters would also, or solely, involve one or more 20mm flak guns which could be very tricky for ground troops. Anyway, here is the German "88" most often encountered.