Crested trig pillars
During World War II, Wynnstay Hall near Ruabon, was used as training establishment for RE [Royal Engineers] Survey Cadre. As part of the practical training, during 1943-47, the trainees built some of the secondary and third order pillars in the neighbourhood. The pillars are unique, they have a RE regimental crest modelled into the pillar sides. The trigs are The Righi (S3094, SJ480575), Mynydd Mawr (S3095 SJ132286), Highash (S3102 SJ566542), Bryn Du (S3109 SJ146359), Ruabon Mountain South (S3111 SJ236457), Selattyn (S3122 SJ255341), Raw Head (S3124 SJ508548), and Gyrn Moelfre (S3128 SJ184293). There are others - Maes-y-Mynach (S3098 SJ234342), Mynydd Myfyr (S3117 SJ243274), Oswestry Station (S3121 SJ296299), Hanging Hill, Shrewsbury (S3123 SJ542134), The Cliffe (S3126 SJ392206) and Foel (S3127 SJ187390) - which have a recess to hold a crest but either it was not installed or has been lost. [from Primary Trigs in Wales by John Davies, ISBN 9781291230482, lulu.com]
There could be others and most likely in the same geographic area.
All crested and recessed (for crests) pillar are in Secondary Block SJ44 (Shrewsbury), within the FB number range S3094 to S3128, and built between October 1943 and early 1944.