[Boatanchors] 51J-4 question

[telegrapher at att.net]

I recently picked up a Collins 51J-4 from a friend to use and decide if
i want to buy it or not.

First of all, it's not a true 51J-4 per my friend.  He said it's an
R-388 that was upgraded by the Air Force to 51J-4 specs.  They added a
product detector on the right side, mounted on a bracket to the support
panel that goes from the front panel to the chassis.  I don't know what
other changes might have been incorporated but it also has 3 filters,
.5, 3.0 and 6.0 Kc.  

The chassis is marked with the tube V and type numbers.  The IF tubes
are 6BE6.  I would not have expected that to be the correct tube but
that's what is marked on the chassis and plugged into the socket.

Not having any 388 information, do these tubes in the IF section sound
like a 388 or what?  These 3 are pretty flat and of all the boxes of
tubes i have, i don't have any of these.  Yet!

Thoughts on the receiver?

Thanks 

Larry
W0OGH