Marlin 81 DL serial number location

[Alan4620]

I just purchased a Marlin 81 DL and I can find no serial number on it anywhere.
I pulled the stock off and looked under there also.24" barrel,hooded front site.
Receiver not grooved for rings,side mount only.Has 2 screws on left rear of receiver for  

Could it be too old to have one? It does not say micro groove barrel either.

Looking down on the top by the bolt there seems to be stamped the letter b,and on the barrel a thin line with an o in it.

It seems to be a great shooter,even though what I thought was a new type of front site was just a wad of dust.Who knew!
 

[J'hawker]

Probably made before 1968 and therefore, doesn't have a serial.  It wasn't uncommon for rimfires to be without serials before then.

[Alan4620]

What about the "micro groove?" My 1957 30/30 has that type barrel.

[jinx]

Pre 57 with no "micro groove. If it has a "beaver tail" forestock and a "S" style bent bolt handle then it's pre war. They didn't make them durring the war. The 2 threaded holes on the left rear of rec. is for a peep sight. Model 21 I think. Don't quote me on the model#. I forget more than I remember nowadays.    They pop up on FleeBay now and then if you want one. With the peepsight installed and in its lowest position it should hit 5"-6" high at 25 yrds. 'cause they didn't have high velosity ammo prior to WWII.
 I have a prewar 81DL too Nice lil' shooter.