[cbuehler]

The tunic has double rows of embroidery on the cuffs and shoulder straps indicating a field grade officer (Major or Lt. Col.).
A bullion embroidered crown for a Major rank would be correct for this.
This tunic was made long enough ago that genuine metal wire embroidery was used, unlike the tacky looking mylar stuff used over the past 30 or more years.

CB
Correction....it appears that the double rows of embroidery on cuffs and shoulder straps are worn nowadays by all officer ranks, whereas previously it was only one for Company grade. Therefore the Star of the Order of the Garter in bullion rank badges would be correct as well.
The apparently have gone to a simplified tunic for all.
Here is the 1920s era tunic of Brig. E.W.S. Balfour CVO, DSO, OBE, MC etc, while as a Major in the Scots Guards, later Col.
Note the quality of the embroidery.