Older Potez XV A2 reconnaissance aircraft, used as trainers, including 428 / A3, 449 / A4, 451 /E1 and 447 / E4. Photo dated 1935 which would just be possible both for the Potez XVs and the Junkers F13s in the background. Cropped photo; the wingtip in the foreground is of 435 / A1. We are grateful for any information about the prewar Polish serial numbers and unit code systems. Photo from: Narodowe Archiwum Cyfrowe

Poland received 110 Potez XV A2 reconnaissance aircraft and XV B2 light bombers from France from 1924. Another 100 A2s were built by Plage i Laśkiewicz and 35 by PWS. From 1927 until about 1935 they were used as trainers and the photo is dated 1935 by the source. We are assuming that construction numbers were used as serials by the Polish military, as in France and Germany. Photo from: Narodowe Archiwum Cyfrowe

Middle part of panorama photo showing a line-up of five Potez XVII aircraft of the Bulgarian army. Towards the left is B-BPEK. Photo from: Lost Bulgaria

The Potez XVII was a variant of the Potez XV reconnaissance aircraft. Six or eight examples were supplied to Bulgaria and based at the main Bozhurishte airfield near Sofia. These military aircraft wore civilian registrations with the B repeated on the tailfin. Left part of a panaroma photo. On the right is B-BPEC. Photo from: Lost Bulgaria