U.P. blow-off/blow-down apparatus

[nobullchitbids]

I'll try this post here, since I am getting no response at MR:

Modern Union Pacific locomotives, and some older rebuilds (including some Harriman mikes) had an unusual, and I think unique blow-down/blow-off apparatus on the engineman's side, consisting of two units (one high, one low on the firebox) joined together by a "Y" pipe which extended into the cab.

My questions are:

1) Did the pipe contain rods for controlling the apparatus in the normal fashion a' la e.g. an Okadee blow-off ****, or did these appliances work on air or steam?

2) (Most important), when retrofitted with such devices, what did the OTHER side of the firebox look like? Did it retain older blow-off cocks? Were they removed? Or did the fireman's side also get the newer devices?

I am building a Pedro mike for a friend, and we have only the engineman's side of 2710 in its post-war years -- our photo of the other side is from the 1930s, before the retrofit.