Autograph baseball question

[Dennis K]

Several years ago I attended an auction. The auctioneer was selling lots from estate sales that he had in the prior weeks that did not sell. One of the items up for sale was 2 signed baseballs. The one baseball was unique. It was signed by over 40 umpires. The ball was neatly signed, as though it was signed at one event where each umpire neatly signed the ball and left space for the others to sign. Would anyone know an event that so many umpires would attend and be willing to sign autographs. And what value would be placed on this baseball. Thanks for your input.
Sorry, I can not get the photos to upload, but these are not stamped autographs.

The umpires that signed are;
Baseball of NL & AL Umpires
L. Young
Wm. Haller
T. McClelland
L. McCoy
M. Hirschbeck
E. Gregg
D. Harvey - HOF
D. Morrison
B. Froemming
G. Crawford
R. Garcia
G. Davis
E. Montague NL 12 #11
J. Layne #24
R. Marsh #30
J. Hirschbeck #17
T. Hendry #35
S. Palermo #14
D. Scott
H. Wendelstedt
J. Brinkman
G. Bonin
J. McKean
M. Winters
V. Voltaggio
J. Joyce
S. Rippley
D. Rennert #16
A. Clark
T. Conney
D. Denkinger AL Umpire #11
D. Coble #3
D. Ford
J. West NL 22
D. Phillips
L. Barnett
G. Kosc
T. Welke
R. Reed
F. Pulli