What is the difference between a Yellow Dot Bleeder and a Yellow Dot? Would it work as a spare ball?

The fabled bleeder. I remember it well. For years there have been a lot of theories
suggested in an effort to explain what actually happened and if in fact, such a thing actually existed at that time. I drilled a lot of Yellow Dots back then. For a long time,
it was the hottest ball on the market--Columbia's answer to the soaker revolution .
The Yellow Dot's predecessor was Columbia's Shur D Pro. Both, the Shur D Pro and Yellow Dot derived their extraordinary hook power from the fact that Columbia developed a softer (polyester) shell that was used on both balls. "Extraordinary hook power" in those days was nothing compared to the hooking power of today's balls, but back then, they were for a time, the "hooking-est balls" made.

Shortly after the Shur D Pro hit the market, the ABC (now the USBC), established
for the first time a minimum ball (shell) hardness rule. For sanctioned league/tournament purposes, the minimum hardness was "72" on the hardness scale. For PBA competition, it was "75". The Columbia Shur D Pro usually averaged
around 65 or so, making its shell softer than the 72 minimum. For this reason, the Shur D Pro could no longer be used in sanctioned competition. For this, Columbia answered with the Yellow Dot--which averaged approximately 77-79 on the scale.
After a while, there arose a batch of Yellow Dots that seemed to hook a little more
than previous (batches).  These became known as the legendary "bleeders" that
have been talked about for years.

It was theorized at the time that the reason these balls had slightly more "hook" than previous balls was because these balls actually leaked or "bled" resin from their shells. In fact, this is still the predominant theory some 40 years later.

Now, there
indeed might have been something factual behind this theory, but I was never convinced that the reason for their extra hooking power was due to this. Back then, what I did learn was that some of the Yellow Dots coming out of Columbia's old San Antonio plant actually measured closer to "75" on the durometer scale, instead of
the average 77-79 like most of the others. I saw this for myself. Consequently, it is my belief that the reason for the bleeders' better performance might have actually been due to the fact that their shells were softer, and not due to resin bleed. The increased
performance was miniscule at best, to be sure. There were still others who always believed that the fabled bleeder was actually a myth that really never existed to begin with. 

The debate goes on.

If I am not mistaken, the Shur D Pro was a Brunswick ball.

I remember both my "O" and "P " series bleeders came out of the box almost a deep red pearl. Over time the color changed to deep solid burgundy. Won't dispute the durometer reads stated above but if we didn't turn the display ball every so often the ball cup would leave an impression in the ball. Had one in the closet for years. When I pulled it out the plastic bag and the ball had fused together.

Sorry to inform you.Yours is not a bleeder. If it was 9R and after it would have most likely been a bleeder. I had the "OP" series when I bowled in junior. Shot my first meaningful 300 game with it when I was 12. That was during the days when someone actually came to certify honor scores. Not the blanket cert now a days.
Check out the garage sales. You might get lucky and find a Bonanza "9R" or "OP" series ball. My team mates Dad bought him a bunch of Bonanza "9R"s. He could crank the crap off that ball. Ya. I'll be 50 next summer.
 Good luck finding a decent cover on a nearly 40 year old ball

I know where there is one in the box undrilled.

Here is a pic of the Bleeder before I put any games on it.

My 1981 bleeder is sitting on the ball rack in my basement. I walked by it this summer and stuff was oozing out of the finger holes and running down the side of the balls.

Nice! Post a pic please.