I think this assumption is correct. All 19th century pieces did not have such a shielded mark. They seem to have started at the beginning of the 20th century. I have just one piece which casts doubt. It is an oval squeeze open snuff box. It bears a shielded 9 which would equal 1909. The snuff box and its elegant engraved initials seems to me to be older than 1909 when most gentlemen had moved on to cigarettes. However, Indian colonial silver did tend to be 10 years behind the times in Europe! I had a quick look and such snuff boxes were seen up to WW1. So, putting away that doubt, I agree with the dating. I have a small Christening mug with mid century angular handle which bears 44 in a shield (= 1944) and is design-appropriate to that date. This must be close to the end of ORR silversmithing in India after 100 years. I hope this helps - Andrew Orr (of that family!)
Here is the inscription on the presentation bowl. The Karachi Sailing Club was founded 1911/12 and the "students" were student officers (all Captains) in the Indian Army Staff College in Quetta about 650 km to the northeast of Karachi, in what is now Pakistan.