International registered letter with perfin “C.H.” in the stamp. The letter is franked correctly with 2 x 25 + 15 = 65 øre, 25 øre (0 – 20g) + 15 øre (for next 20 g) was the rate for International letters 2nd class from January 1st 1927 to October 31th 1933 and the rate for registering was 25 øre from April 1st 1926 to June 30th 1940. The stamp is cancelled February 28th 1931 with København 3 Nr. 11a Kjøbenhavn 1. 3. Bro IIIc.
This letter is the only known documentation with the user Carl Holbek & Co Ltd all other is with P. & S. plum Ltd, it is also the earliest known use of the perfin C.H.