Tony
I don't want to turn this into an argument.
SHT had delivered as new works nos. 1053, 1105 and 1522 in 1906/8/15 as SHT nos. 11,12 & 18.
P & M had delivered as new works nos 1054, 1179, 1328 and 1449 in 1907/12/13/16 as P & M nos. 11,12, 3 and 4.
Sources are various - but among them Railway Bylines July 2004, GWR.ORG.UK, Wiki etc. which I will admit are not primary sources but are consistent with other respected authorities - e.g. RCTS Locomotives of the GWR part 10. P & M never had a loco no.13.
Cheers
Dave