Proper plural form

I am wondering what the proper way to make acronyms plural is.

for example…

Distribution List = DL
Distribution Lists = DLs or DL’s

My usage guide would recomend DLs on the grounds that the apostrophe would indicate missing letters in this context, but that’s already implied by the fact that DL is an abbreviation anyway - after all you don’t write D’L’ do you?

everton is right, DLs would be correct. However, you often see the plural as DL’s (incorrect).

I remember being taught that they use an apostophe in the plural, thus “Sale on TV’s and stereos” would be correct. It can be especially important when using all caps–TV’S is different from TVS, which could mean thermal vacuum switch.

Now for the real puzzler: if the plural of TV is TV’s, and the possessive of TV is TV’s, what’s the plural possessive of TV?

Tech writer chiming in here…

<typical Canadian usage>

Acronyms are capitalized without periods. An s indicating a plural form remains uncapitalized. No apostrophe is used.

Thus, the plural of TV is TVs, not TVS (note difference in case).
The TVs were all on, blaring out an ad for the new TVS (thermal vacuum switch) from Acme Industries.

The plural posessive is TVs’ (the apostrophe follows the s, as in other plural posessives).
All of the TVs’ volume controls were not working. The sales staff were rapidly getting headaches.

</typical Canadian usage>

TVs’

IIRC, possessive words ending in ‘s’ just take an apostrophe - no extra ‘s’.