The Special Delivery service (and stamps) were introduced in 1885.
The Postal Laws & Regulations stated that both services could be combined, but that all tracking and control for both services were to be followed.
A question was recently raised by a member of my Registered Mail Study Group as to how frequently were these services combined in the early years of Special Delivery, say 1885 - 1900.
The Annual Reports of the Postmaster General provide statistics for both the domestic registered mail and special delivery service individually, but are silent on their use in combination.
For 1893 (midpoint in my range), records show there were 11.7M domestic registered letters and 2.8M special delivery letters.
Does anyone have a thought on where such a statistic might be found? Or estimated?
My instinct tells me this was not a frequent combination, and Henry Gobie, in his book
The Speedy does illustrate several such covers, but he does not comment on frequency.
To check my theory, I went to my several albums of Texas Registered Mail. To my surprise I found nothing from the 19th century, and only ONE !!! Registered Special Delivery cover from 1909, within my primary window of interest 1865-1920.
from 1909...

Since "Plan A" was not productive, I went to "Plan B", eBay.
From 1898...

From 1913...

From 1914...

Seeing these eBay results, I checked my census of Texas registered covers with Scott F1, which I have maintained for nearly a decade. None of the covers there were both Registered and Special Delivery.
Can anyone add to this discussion?
Mike