I have seen this panto before, but it was on this same frame when it was listed on eBay (a few years back?) so not much help there. I do remember it being advertised as having a French threaded bb shell.
I only have a very flimsy guess as to the origin of the panto and a slightly more solid guess on the origin of the frame.



TL;DR

I'm guessing this frame was likely part of a small run that came out of one of three shops: Macario, Candela, or Marotias, possibly for Lorenzana (a Madrid shop involved in racing in the 80s).


Long version

This is an interesting puzzle to untangle.


First off, I agree that the Cosme decals look younger than the paint and weren't there originally. The decals themselves are indeed of the shop in Alcobendas near Madrid (as T-Mar posted), so not related to Cosme Saavedra.

side note: For some reason, the shop's website (under ¿Quienes Somos?) only mentions that they're a northern Madrid shop that's been in business since 1985. It's only if you look at their Facebook page do you find the connection to a builder, Cosme Díaz, who worked with Macario Llorente for 47 years. It seems like the person running the Cosme shop is Cosme's son (judging by the pic descriptions). Here are some pics of Cosme working:





Was Cosme Diaz himself involved in starting this shop or was it only named after him? I don't know. Might be worth contacting whoever is currently in charge to get the scoop.



As for the distinctive frame features, we've got the panto, the seat stay caps, the clover-like cutouts, the stay ends and numbers stamped on the chain stay nozzles of the bb shell.


Clover cutouts:

Although you'll also find similar cutouts on some British marques (like Ellis-Briggs and Mercian) or Italian ones like Grandis and CBT Italia, I'll focus on Spanish builders here.
Of the ones I'm familiar with, Macario Llorente is the first that comes to mind. This feature wasn't used very frequently so there isn't a ton of examples online but you can find a decent number of frames with these cutouts, ranging from the 60s to the 80s.

The other Spanish marque that I've seen these on is Candela (of Madrid). The Candela brothers built high end frames in the 50s and 60s but there are very few examples online (I have pics of only two). I don't know how long they were in business, but they were building frames at least as late as early-mid 80s, according to some sports newspaper articles. And guess who learned his craft at the Candela shop? Macario Llorente.


Macario:




This Macario is claimed to be built by Marotias:




Candela:






Seat stay caps:

Most people will probably associate this style of stay caps with Bernard Carré. However, I think this is a Spanish built frame, even though the threads might be French.

I've not come across a Macario labeled frame that had seat stay caps exactly like the mystery frame, though. There are some with semi-wraparound stays (that owners/sellers attributed to Cosme Díaz) but are not a match:





One Spanish builder who did do stay caps like the mystery 'Cosme' was Jose Maria Marotias. He's a very well regarded builder and relatively well known both in Spain and abroad (he built frames for Merckx and Ocaña).
Here are the seat stay caps on some of his frames (top left is from Luis Ocaña's 1969 bike and the top right José Manuel Fuente's ('El Tarangu') 1972 bike):





I'm not sure what relationship Marotias and Macario had. I have seen some frames that were claimed to be by Marotias even though they had Macario decals. However, I have also seen Otero frames with Macario decals, so I'm not entirely sure what to think of this. The fact is that the stay caps on the mystery frame come closest to what Marotias used to do.




The panto:


While the "L" in the panto might refer to "Llorente," I've never seen any "L" logos on any Macarios nor have I seen any star-like logos.
The only Spanish cycling logo that comes anywhere close to this panto is that of a company called Lorenzana from Madrid.
Apparently, there were several Lorenzana brothers who were in the moving business who also operated a bike shop in Madrid. I've only seen a few bikes labeled Lorenzana along with some accessories. I've never seen a panto on a frame, only stickers, and while not a match, the concept is similar:






The Candela built frames from the 80s (that I mentioned earlier) were the ones built for the Dormilon racing team, around 1983/4, and were badged Lorenzana:




There is a Rafael Lorenzana who was a pro rider in the late 80s/early 90s (for team Puertas Mavisa) who manages a moving company but is still active in cycling. Would be interesting to get some background info on this from him.