Under Dash Panel - Left Side
I've had my panel out for awhile waiting to put replace the foam insulation material backing... so it was easy to make a direct out of car comparison with the pic of your's you posted.
Bottom line is your panel looks unlike mine. My best guess (based on below) is that your panel isn't for the under-dash area on the left side of steering column. FYI, the fold line is at the fire-wall end of panel... the short folded section sit's roughly against the firewall padding, the rest of the panel under the dash itself... but your panel's missing a bunch of cut-outs required for clearances, so doesn't appear to apply to the 113 chassis under dash left side.
A suggestion: Go to someone / car lot that has a 113, borrow their panel... lay it over yours, line up the circular holes and at least one edge simultaneously, then trace the other panel's outline onto yours... then use the appropriate sharp cutting tool(s) (or fasten a punch --- ha ha) to cut a correct fitting panel from the panel material you have now. If that isn't possible, have someone send you a paper cuttout of their panel to use as a pattern... or find one at some MB classic part's dealer.
A pic's worth a thousand or so words, but it's a lot more trouble to get a pic of my panel, and time consuming for me to get it posted, so words will have to suffice.
My Panel:
1) Overall Length, including folding section = 17.5 inches; Width = 12.75 inches. Length between fold-line and edge opposite = 13.5".
2) Hole Diam = 3 inches; Centerline 4" from one edge, 2 3/4 " from th other edge. Your hole appears to be in the same location on your panel.
3) There are 5 other basic cuttouts in the otherwise roughly rectangular shape --- I'll describe them going from 12 o'clock in clockwise direction with the outside of the panel facing upwards toward you and the folded edge at the 12 o'clock side... i.e. furthest from you.
a) 12 o'clock: Oblong notch, 1 5/8 inch. wide for the brake. Notch/Slit's long direction is perpendicular to the fold line. Notch has a rounded end (not squared off) with radius = 1 5/8" divided by 2 (whatever that is) & ends 6" from the fold line.
b) 3 o'clock: On the side edge closest the circular hole there's a cuttout along the edge... 2 3/4 inch long (along the edge) x 1.5 inch wide (into the body from the edge). This is to let the cable from the hood release handle pass from under (outside) the panel to above it on the cable's passage to the firewall.
On the side opposite the b) cuttout for the hood release cable, there are 3 other notches or slots:
c) 7 o'clock: On the corner (intersection of the edge furthest from the fold line & side opposite notch b), there's an approximate square cutout 2" x 1 3/4" from each edge....i.e. the actual 'corner' of rectangle has been cut out on that corner. This corner is the one closest to the steering wheel... but I can't describe why exactly it's there... it makes my panel fit up nicely against the steering column at that location though.
d) 8 o'clock: Moving up the edge from that corner, there's another slot/notch 1" wide x 3" deep into the panel (long dim of notch perpendicular to the side edge). This notch also has a radius end... 1/2" radius ('full' radius if you're a mechanical engineer). This notch/slot is to let the wire harness exiting the steering column pass outside the cover (for the length of the fold in the harness) since the harness actually interferes with the placement of the panel at that location ... hence this notch lets the harness fold out and back without interferring. It's possible that this notch/slot doesn't need to be there on later model's (or earlier ones perhaps... mine's a '67 250SL about mid-way thru the 250 build series) if the wire harness exits your steering column either further under the dash or in a completely different manner.
e) 10 o'clock: The 'last' of the 5 cutouts is on the next 'corner' up from slot d) (in direction toward the fold line)... it's also a 'corner' cutout 2" x 3"... i.e. 2" into the side, and 3" long (along the edge). But the start of this cutout begins 2 3/4 inches from the edge of the slot d)... and ends 3" further up. That's also the 'top' edge of the panel on this side, with the remaining cutout area for the clutch (next to the slot for the brake). This cutot fits next to the steering column under the dash... side opposite the circular hole. This corner cut is to let the steering column pass from above to below the panel as the column "cuts thru" the panel at this location.
Tha ends my description of my original panel on the '67 250SL... but I can easily imagine some modifications which would depend on actual configurations of wire harness's designs and brackets under the dash.
What I can't fathom though is how the folded edge end of your panel can allow the brake and clutch to pass from their pivots above the panel to their foot pedals... since you have no slots or clearance features on your panel for same.
I'm judging the size of your panel's length from fold to end by the number of diam's of your hole... being about 5 to 6 hole diams from end to fold-line. If your hole is 3" diam as mine is, then the length of your panel is about 15" to ~17" in it's long dimension from driver's edge to firewall fold line. This is at least 2 if not 3" longer than mine for that dimension, and mine fits flat (relatively) between the underdash metal edge nearest the driver (with a slight overlap) and the firewall padding. This implies that a 113's underdash panel area are about the size indicated by my panel --- since my panel fits nicely and securely in that area.
If your hole's 3" and my estimates of your panel's length is right (front edge to fold-line), and there's no cutouts to let the brake and clutch pass, then perhaps your panel is't from this car... i.e. not a 113 chassis under-dash panel.
But... since I've only examined my panel carefully and no others from any other 113's, this is just my conjecture without any other foundation than I described above.
Longtooth
67 250SL US #113-043-10-002163
95 SL500