Found this info online, hope it helps
HOW TO IDENTIFY JE/SRP PISTONS
All JE and SRP Pistons will have "JE" or "SRP" forged or laser engraved on the underside of the piston. If your piston does not have these marks, it was not manufactured by JE or SRP Pistons. Please use the information below to identify your piston.http://www.jepistons.com/Images/TechCorner/identify.jpg
Job # : This 6-digit number is located on both custom and off-the-shelf pistons. Use this number to reorder custom pistons and/or locate replacement components for custom pistons (wrist pins/locks/rings).
Shelf Piston Part # : A 6-digit number beginning with P/N indicates an off-the-shelf, catalog item. Use this number to re-order off-the-shelf pistons. Custom pistons will not have this number.
Forging # : This number ONLY identifies the raw forging that was used to manufacture the piston. A large variety of bore sizes, compression heights and other design features can be applied to a single forging.
Frequently Asked Questions
What if my piston has no laser mark?
Pistons manufactured before 2004 did not have any laser marking and must be identified by another method. If the pistons are in the original box, there is a label located on the side of the box that identifies the job number and the piston part number. If you do not have the original box, try to locate the original JE/SRP invoice.
If you have no documentation for your JE or SRP Pistons, you can mail a sample to JE Pistons to reverse engineer. If you’re sample is followed by an order for a set of pistons, there is no charge for this service. NOTE: If no order is placed, there is a one-time $75 layout fee for this service. Please allow 3-5 days for reverse engineering.
If you would like JE to reverse engineer your piston, please mail a single sample piston, your contact information and a method of payment to:
Attn: Piston Identification, Engineering
10800 Valley View Street
Cypress, California 90630
I have located the job/order number, now what?
If the piston only has the job/order number on the pin boss, it is a custom piston. If you want to place an order for custom pistons, you can call the JE Pistons technical sales department or a JE Pistons distributor. Provide the 6-digit job/order number and list the features you would like to change (bore, compression distance, etc.) on the custom piston order form located here.
I have located the Shelf Piston Part number, now what?
You can order replacement pistons and accessories from your JE Pistons distributor or directly from JE Pistons by adding the item number to your shopping cart.
Online Shelf Stock Order Form (existing customers):
Order Desk: Tel: (714) 898-5114
FAX: (800) 5PISTON firstname.lastname@example.org