Karen Dinicola (asker) Sep 10, 2021:

Thanks to all OK, my time is up. For lack of a more definitive answer, I will be leaving this one as U.L. Thanks again to both for your valuable insights!!!

AllegroTrans Sep 10, 2021:

Which perhaps indicates that these are technical reference numbers common to all (or at least many) consumers

AllegroTrans Sep 10, 2021:

Asker, what you didn't tell us is that these abbreviations and numbers seem to be immediately preceded by the consumer's name and address.
I found a specimen bill on the web and it contains exactly the same numbers as you posted. See:

ANA MERCEDES ASUAJE DE RUGELES
DISTRITO LIBERTADOR MCPIO. LIBERTADOR PARR. EL RECREO 1050 URB. FLORIDA NORTE 050301411 AVENIDA DON BOSCO CRUCE CON AV AVILA EDIF CHAPULTEPEC PS. 04 APTO 7 7 POSTE 03EM 435 Aparato: 100903649 U.L.: CRA56015 O.C.: 18000030298

Karen Dinicola (asker) Sep 10, 2021:

POSTE 03EM 435 Aparato: 100903649 U.L.: CRA56015 O.C.: 18000030298

Orden de contrato would be a possibility, except for that this number would probably change on other people's bills, and in this case it doesn't.

AllegroTrans Sep 10, 2021:

Could you tell us what are the three numbers please?

AllegroTrans Sep 10, 2021:

"orden de contrato" perhaps?
Also I found a sort of explanation of their bills at https://www.notilogia.com/2019/09/corpoelec-consulta-de-sald...

Karen Dinicola (asker) Sep 10, 2021:

Now thinking "O.C" might be "obra civil" for "public works."

Karen Dinicola (asker) Sep 10, 2021:

On further reflection, I don't think O.C. is purchase order, because I have found other examples of the same bill for other customers, and the numbers for both "U.L." and "O.C." don't change, so it must be some kind of a standard thing.

Karen Dinicola (asker) Sep 10, 2021:

Both of these suggestions are possible. On the one hand, UL for "Underwriters Laboratories" is a global company overseeing the safety of electrical devices, so that is entirely possible. It has the advantage of being the same in the source and target languages, so if it turns out to be wrong, at least it would be easy to trace to the original. I have also considered the possibility of "unidad de lectura," as in "display unit." So, also possible. I am thinking "orden de compra" or "purchase order" for O.C., given that it is a bill. I just wish that I had more evidence to trace these acronyms to this particular company. Good thoughts, though!

AllegroTrans Sep 10, 2021:

Context Is the number an electrical measurement? What have you deduced for "O.C."?

philgoddard Sep 10, 2021:

The U could be unidad.