You have what appears to be a set of holes for Unertl blocks.
The spacing for the rear block is .860 and the front block spacing is .560 with the blocks 7.2" apart, center to center. 
The best place to obtain scope blocks is from Steve Earle. As for obtaining a Unertl scope, You could try gun shows or Ebay, but hang onto your wallet.

Steve Durren

Those measurements will work with any number of target type scope bases and scopes. Lymans, Unertls, Feckers, Litscherts, etc. all accept mounts with similar spacing. I have an old Stevens Schuetzen Jr. with Stevens scope, and the same spacing between mounts, and hole spacing.
Probably find that the higher the scope magnification, they usually spaced the mounts a little farther apart. Most of the higher power scopes used a 8.5"-9" spacing, while the 7.5" is more common on 10x or less.
Good luck!

The 7.2" dimension is not arbitrary, as Dale states, it's there for a specific reason. It's also true, however, that the larger higher-power Unertls as well as many of the much older scopes frequently have a wider base spacing due to their greater length. You should see how ridiculous my Borchardt looks with the 7.2" spacing and the big 2" Unertl on top of it! There's hardly room for the recoil spring, & the scope tube looks like it might bend from all that unsupported weight out front!

Your Pope barrel should be fitted with bases that will accept the Winchester A5 rings as well as the Unertl/Lyman type. These bases can be identified by noting the little indentation in the base on the side opposite the little half-moon cut. The half-moon cuts are for the common Unertl or Lyman or Fecker or Litschert rings which use them for a locating point, and the little indentations serve the same purpose for the Winchester A5 scopes as well as some other early ones. The indentation will be fairly shallow (~1/16"-3/32") and centered on the base front-to-rear & top-to-bottom, exactly opposite the half-moon cut on the other side. Many early Unertl-type bases have these little indentations but most later-manufacture bases do not.

The little indentations can be added by a careful workman using a pointed carbide burr in a hand grinder, but please be advised that some of these target scope bases are as hard as woodpecker lips!

Your Pope barrel was made during the time when many if not most scopes used the little indentations for location, and so those type bases would be the most appropriate for your rifle and would not give up a thing to the more modern ones.
Good luck, Joe

Yes, I know the reason for the spacing, but out of the 6 old scoped singles I own, only one has that spacing. The others all use a 8.5"-9" spacing. These were all scoped, or tapped for scopes when they came to me, so someone else decided the longer, larger tubes wouldn't work with the 7.2" spacing.
Actually one is tapped much farther apart, but it's for a full length Malcolm type tube.

CRK, your Pope rifle is drilled and tapped for the standard spacing that will give 1/4 minute clicks or 1/4" shift at 100 yds. Another spacing that was common was 12 1/8" inches
(Memory?) that gave 1/8 minute clicks. We also have to remember that for many the spacing had to do with the scope at hand. There were some variations that were common.
Stevens for example made a series of 30" long scopes, not full length but long enough to require longer spacing. I have a Schoyen Hiwall that is tapped for these scopes. The other issue is where the holes would land. I have seen rifles drilled and tapped in an odd spacing just so they would not land on the barrel stampings. On a Winchester Hiwall the 7.2 spacing wants to land right in the factory stamping. When Winchester recieved an order for a Rifle drilled and tapped for scope blocks, they would stamp the factory legend  and the caliber designation at the 10:00, ten O,clock position on the barrel so they would not have to drill into the lettering. I just bought one done in that way. As to Scope Blocks? Steve Earle of Plymton Mass. offers them in 4 0r 5 different heights  and with the correct screw hole spacing. His blocks are cut for both the modern scope clamp as in Lyman and Unertle but also have the left hand "Dimple" 
for the early Scopes such as the Winchester A-5 or Lyman 
5-A and the Stevens line of scopes. He advertises in both the 
Single Shot Exchange and the ASSRA Journal. His quality is top notch. And he supplies a set of brand new screws with each set of blocks. They are not easily found outside of gun circles as the size is 6-48. HTH and wishing you success with you Pope Rifle. Regards, FITZ.

CRK, I agree completely with MP. As an example. Many years ago Paul Shuttleworth used to visit my club when he was in the area. He stated to me and I quote. "The old Telescopes are nice to have if you wish to have a complete outfit from the era. But if you wish to be really competitive buy a modern scope such as a Lyman or a Unertle" my own experience has been the same as MP. I started wanting Winchester A-5 scopes. Then I came into a Lyman A-5 and realised the optics were superior to even my best Winchester A-5. Then on looking them over I discovered the difference between a Rolled guide groove in the tube as Winchester had
and a real Pope Rib a rectanguler guide on the outside of the tube that alligned the scope. My favorite Telescope's became the Lyman Super Targetspots. Not because of any Optical issues but because their greater length gives me more latitude as to fore and aft adjustment. many feel that Unertle Scopes have better optics and I would not argue about that because I really don't know if they are or are not better. HTH,
Regards, FITZ.