The maximum wearable was four, if [unlikely but not impossible ...... I know of no cases but you can bet they existed!] a 1914 or 1915 soldier or RM was discharged and then went to sea.
I have certainly seen WW1 groups of four, but these were awarded to members of the RNR, some of whom qualified for the 1914-15 Star and Victory Medal in addition to the usual Merchant Navy entitlement of the Mercantile Marine medal and the British War Medal.