I have a Weathertron BAY28X138A mercury switch thermostat (~30yrs old) with one heating and one cooling lever. Trying to replace with the Honeywell RTH2300B programmable thermostat. The wires on the Weathertron are as follows:

G-Green
Y-Yellow
X2-Black
B-Blue
W-White
T-Tan
R-Red
O-Orange
U-not connected
F-not connected

There are four contact switches on the back of the mercury switch face. One the cooling side, tan is connected to one switch, red to the other. One the hot side, red and tan to one and just one post of the mercury switch soldered to the other. There are 3 common posts on the back. White to the post on the cool side, black to the post at the bottom. On the wall one switch contacts red the other one contacts orange. The common post on the hot side contacts the tan post. The common post on the cold side contacts white. The X2 or black at the bottom contacts the center post on the wall and not sure if grounded or connected to something else on the backside of wall mount. I have pictures but cannot send through this format. In any case, what do I connect to the back of my honeywell which has O/B, Y, R, G, W?