find the differences

[Brian B-P]

... 2nd are the very low contour lights. Correct, those are mandatory overhere. Amber to the sides, white to the front and red to the back.

Excellent - I learned another new thing today: white lights facing forward on European trailers. I had not noticed that before.

A 2nd frame was build under the original, the tubing used is a bit bigger in diameter and a bit thicker in materials, resulting is a stiffer frame. Ir=t was welded to the original from front to back, including the axle.
The original bolted on coupler was removed and replaced by a welded on one, from extra stiff material.

Wow, the frame reinforcement is an extreme modification compared to what was expected. It does make sense to me that the extension of the pinbox/tongue/boom would cause more flex in the frame. Undamped flex would mean bucking.

Is the original frame constructed of the 1.5" x 3" (38 mm x 75 mm) tubing originally used by Escape on all single-axle models, or did this trailer have the larger 2" x 4" (50 mm x 100 mm) tubing used on all tandem-axle models (including the 5.0TA which replaced this model)? My guess is that the original was 1.5" x 3" and you have added 100 mm (4") wide tubing to it. Since they are stacked, rather than side-by-side, the result will be far more than twice as stiff.

The reinforcement is not just added to the original, it is different in design: it is an A-frame extending forward from the vertical sections, rather than the original rectangular box. While the box must be there to support the upper section of the body, it makes sense for this addition to connect the verticals to the tongue (or boom) more directly.

It would be interesting to see the section of reinforced frame under the trailer floor, and especially around the suspension (axle) mounting area.

How much mass (weight) did the frame change add?