Hi David, the first 3 planes were put together with 3 Macchi-41 after their arrival in Mallorca in december 1936, forming the group 2-G-62, based at Pollença, so all the planes had the code 62 in their numerals, 62-1 to 62-3. They were handed over to Spaniards after a month of service.
The gabbiano 62-1 crashed into a ship mast, killing the pilot Ruiz de la Puente and his crew in february 1937. In march 1937, 5 more Cant-501 arrived to reinforce the group, being numbered 62-4 to 62-8.
In august 1937, they worked together with 3 Italian gabbianos based in Sardinia, in their observation role. After all, Italians were violating systematically the non intervention pact already...
In march 1938 they were combined into group 2-G-62-70 with the Dornier Wall and in september 1938 the 6 Cant-506 substituted the D-W, becoming the group 2-G-62-73.
Along all this time, they spotted lots of transport ships carrying material for the Republicans and also made dozens of observation flights over Republican ports, flying at 4000 m to avoid AAA.