Perhaps replace the overlook structure entirely with a turret on a platform that is raised and lowered out of the armoured box of the caboose?
Been poundering. You're up in the mountains at a mine, you have to get gold to the railhead. What do you have to work with? There's probably a carriage maker and wheelwright in town, if not actually on the mining company's payroll. The best source of armor is probably an old, clapped out mining steam engine (little choo choos). Looks like this -
So how do you mount a turret, when most were fitted with ball races? Turn a (lighter than a wagon) carriage wheel and axle on end, then hang that drum of locomotive boilerplate on it.
The main gold storage box can be an armoured pannier under the frame, further lowering the CG.
Gold mines produce a rough product called a Doré bar. This is not an ice cream dessert but a semi-pure alloy of gold and silver (typically about 80 percent pure gold and weighing up to 25 kgs). The gold is then sent to a refinery, where it is refined into gold of different forms and purity.
For purposes of this production, we'll assume the standard wagon load is one half ton (US short), or twenty 50 pound Doré bars (containing 12,800 ozs of gold and 3,200 ozs of silver). That's roughly $256,000 of gold and $3,200 of silver (if they were pure) in 1885 exchange rates. Assuming dross & imperfections, maybe $250,000 all told?
According to the United States Mint, a standard gold bar measures 7 x 3 5/8 x 1 3/4 inches & weights about 25 pounds. So a 50 lb Doré bar would be roughly 7 x 3 5/8 x 3 1/2, more or less? A stack of 3 x 3 bars would still be less than one cubic foot, so 50 bars would probably fit within a 50 cubic foot storage area.
